This document discusses motion and time. It begins by defining different types of motion such as linear, circular, and periodic motion. It then discusses ways to measure time intervals from days to microseconds. Clocks use the periodic motion of pendulums to measure time. The document also defines speed as the distance traveled divided by the time taken. It provides examples of measuring the speed of moving objects and compares speeds of different animals and vehicles. Speedometers are introduced as devices that can directly measure the speed of a moving object.
This document discusses kinematic equations and concepts related to motion including velocity, acceleration, displacement, time, momentum, kinetic energy, and potential energy. It provides the key kinematic equations:
s = ut + 1/2 at^2
v = u + at
Where s is displacement, u is initial velocity, v is final velocity, a is acceleration, and t is time. It notes these equations require constant acceleration. Graphs are more useful when motion is irregular. It also discusses concepts like acceleration due to gravity, components of velocity, momentum, kinetic and potential energy, and power.
MOTION Class IX PowerPoint Presentation Arpan Bose
1. Motion is defined as a change in position of an object over time relative to its surroundings. An object is said to be at rest if its position does not change over time relative to its surroundings.
2. Motion can be classified as translatory, rotational, or periodic. Translatory motion involves straight-line motion, rotational motion involves motion around a fixed axis, and periodic motion repeats over regular time intervals.
3. Physical quantities can be scalar or vector. Scalar quantities only require magnitude, while vector quantities require both magnitude and direction. Examples of scalars include mass and time, while examples of vectors include velocity and displacement.
The document defines and explains key concepts related to motion including distance, displacement, speed, velocity, and acceleration. It provides equations and examples to calculate speed, velocity, and acceleration. Speed is the distance traveled per unit of time. Velocity includes both speed and direction of motion. Acceleration is the rate of change of velocity with respect to time. The document uses graphs and calculations to illustrate these concepts.
The Heart Science 7th class powerpoint presentation10NEEL10
The document summarizes the key parts and functions of the human heart and circulatory system. It discusses how the heart is a non-stop muscular pump with four chambers that pushes oxygenated blood through arteries and returns deoxygenated blood through veins. The left side of the heart is larger and more powerful as it pumps blood through the entire body, while the right side pumps blood to the lungs to receive oxygen before returning to the left side. With each heartbeat, the heart vigorously contracts ("lub") to push blood out and relaxes ("dub") to refill in its continuous cycle to circulate blood throughout the entire body.
The document discusses various concepts related to motion including:
- Motion depends on the point of reference used and can be relative.
- Distance is the total length traveled while displacement is the straight line distance between initial and final positions.
- Speed is the rate of change of an object's position with time, while velocity includes both speed and direction of motion.
- Acceleration is the rate of change of velocity with time and can be positive (increasing velocity) or negative (decreasing velocity).
- Graphs of displacement vs time and velocity vs time can provide information about an object's motion like speed, acceleration, and distance traveled.
Light travels in straight lines until interacting with objects. It can scatter, reflect, refract, or be absorbed. Reflection causes light to bounce off a surface at the same angle. Refraction causes light to change speed and direction when passing from one medium to another, such as from water to air. Absorption occurs when light is taken in by an object and its energy is transferred to heat.
This document discusses different types of motion. It defines motion as a change in an object's position over time and notes that motion is always observed relative to a reference point. It then outlines the main types of motion as translatory, circular, random, oscillatory, vibratory, and periodic motion. Translatory motion is described as uniform motion in a straight line and can be rectilinear or curvilinear. Circular motion involves moving around a fixed axis, with examples given of revolution and rotatory motion. Several everyday objects and actions demonstrating multiple types of motion are provided.
This document discusses kinematic equations and concepts related to motion including velocity, acceleration, displacement, time, momentum, kinetic energy, and potential energy. It provides the key kinematic equations:
s = ut + 1/2 at^2
v = u + at
Where s is displacement, u is initial velocity, v is final velocity, a is acceleration, and t is time. It notes these equations require constant acceleration. Graphs are more useful when motion is irregular. It also discusses concepts like acceleration due to gravity, components of velocity, momentum, kinetic and potential energy, and power.
MOTION Class IX PowerPoint Presentation Arpan Bose
1. Motion is defined as a change in position of an object over time relative to its surroundings. An object is said to be at rest if its position does not change over time relative to its surroundings.
2. Motion can be classified as translatory, rotational, or periodic. Translatory motion involves straight-line motion, rotational motion involves motion around a fixed axis, and periodic motion repeats over regular time intervals.
3. Physical quantities can be scalar or vector. Scalar quantities only require magnitude, while vector quantities require both magnitude and direction. Examples of scalars include mass and time, while examples of vectors include velocity and displacement.
The document defines and explains key concepts related to motion including distance, displacement, speed, velocity, and acceleration. It provides equations and examples to calculate speed, velocity, and acceleration. Speed is the distance traveled per unit of time. Velocity includes both speed and direction of motion. Acceleration is the rate of change of velocity with respect to time. The document uses graphs and calculations to illustrate these concepts.
The Heart Science 7th class powerpoint presentation10NEEL10
The document summarizes the key parts and functions of the human heart and circulatory system. It discusses how the heart is a non-stop muscular pump with four chambers that pushes oxygenated blood through arteries and returns deoxygenated blood through veins. The left side of the heart is larger and more powerful as it pumps blood through the entire body, while the right side pumps blood to the lungs to receive oxygen before returning to the left side. With each heartbeat, the heart vigorously contracts ("lub") to push blood out and relaxes ("dub") to refill in its continuous cycle to circulate blood throughout the entire body.
The document discusses various concepts related to motion including:
- Motion depends on the point of reference used and can be relative.
- Distance is the total length traveled while displacement is the straight line distance between initial and final positions.
- Speed is the rate of change of an object's position with time, while velocity includes both speed and direction of motion.
- Acceleration is the rate of change of velocity with time and can be positive (increasing velocity) or negative (decreasing velocity).
- Graphs of displacement vs time and velocity vs time can provide information about an object's motion like speed, acceleration, and distance traveled.
Light travels in straight lines until interacting with objects. It can scatter, reflect, refract, or be absorbed. Reflection causes light to bounce off a surface at the same angle. Refraction causes light to change speed and direction when passing from one medium to another, such as from water to air. Absorption occurs when light is taken in by an object and its energy is transferred to heat.
This document discusses different types of motion. It defines motion as a change in an object's position over time and notes that motion is always observed relative to a reference point. It then outlines the main types of motion as translatory, circular, random, oscillatory, vibratory, and periodic motion. Translatory motion is described as uniform motion in a straight line and can be rectilinear or curvilinear. Circular motion involves moving around a fixed axis, with examples given of revolution and rotatory motion. Several everyday objects and actions demonstrating multiple types of motion are provided.
This document discusses motion and how it is described. It explains that motion can be linear, circular, rotational, or vibrational. Linear motion along a straight line is the simplest to describe. Position is described relative to a reference point, while displacement is the straight-line distance between the initial and final positions. Distance refers to the total path length traveled, which can be different from displacement. Uniform motion means equal distances are covered in equal time intervals, while non-uniform motion means unequal distances are covered. Speed is the distance traveled per unit time and gives only the rate of motion, while velocity also considers direction of motion. Average speed and velocity can be used to describe non-uniform motion.
Straight Motion Regular Report by Fildia PutriIndy Puteri
The document describes an experiment on straight line motion. The purpose was to understand the difference between distance and displacement, determine speed and average speed, and investigate the relationship between displacement and time for objects moving in a straight line with constant speed. Students measured the distance, displacement, and travel time of three objects moving along three different tracks using a meter and stopwatch. Data was also collected for a bubble rising in a vertical glass tube at different distances, measuring the travel time. The results showed that objects with higher speeds took less time to travel the same distance, and objects placed higher in the tube moved faster between points.
This document discusses motion, speed, and time. It defines motion as a change in an object's position and speed as the distance covered by an object per unit of time. Uniform motion has constant speed while non-uniform motion has changing speed. Time is measured using periodic events like the sun's motion or a pendulum's oscillations. A simple pendulum's time period is the time taken to complete one oscillation. Distance and time graphs can represent motion, with uniform motion shown as a straight line.
The document summarizes some key aspects of Einstein's Special Theory of Relativity in an entertaining way. It explains that (1) nothing can travel faster than the speed of light, which is constant for all observers; (2) as objects approach the speed of light, time slows down, length contracts, and mass increases to account for the constant speed of light; and (3) these effects have been observed in particle accelerators where particles swell in mass as they near the speed of light.
1) The document discusses Newton's laws of motion and concepts related to motion including velocity, acceleration, uniform and non-uniform motion.
2) It defines key terms like displacement, distance, speed, velocity, uniform and non-uniform acceleration.
3) Newton's laws of motion are summarized - including that a body at rest stays at rest and a body in motion stays in motion unless acted on by a force, and that acceleration is directly proportional to force.
This document defines and explains key concepts related to motion, including:
- Motion is defined as a change in position over time. A point of reference is used to measure an object's changing position.
- Displacement refers to the straight line distance and direction between two positions, while distance is the total path traveled.
- Speed is defined as distance divided by time and can be measured in units like km/h or m/s. Speed with direction is called velocity.
- Instantaneous speed is an object's speed at a moment in time, which may vary, while average speed represents the speed over the entire journey. Constant speed means the instantaneous speed does not change.
- A
The document discusses motion and force, covering distance, time, speed, and forces. Chapter Twelve focuses on distance, time, and speed, defining key terms like speed, velocity, constant velocity, and average speed. It explains how scientists describe motion using measurements of distance, time, and speed, and how these values are related through equations.
The document discusses various concepts related to motion including:
1. Motion is defined as the change in position of a body with time. It can be described by distance travelled and displacement. Displacement refers to the shortest distance between initial and final positions along with direction, while distance travelled is the actual path length.
2. Uniform and non-uniform motion are defined based on whether equal distances are travelled in equal time intervals. Distance-time and velocity-time graphs are used to represent motion.
3. Key concepts like speed, average speed, velocity, average velocity, acceleration, uniform and non-uniform acceleration, retardation, and equations of motion relating these quantities are explained.
4. Circular
This document provides an overview of the module on the laws of motion. [1] It will cover description of motion, causes of motion, and forces and equilibrium. [2] Students will learn about concepts like distance, displacement, speed, velocity, uniform velocity, uniform acceleration, inertia, and Newton's laws of motion. [3] They will complete activities to explore these concepts hands-on and apply their understanding.
This document contains a table of contents for a science textbook. It lists 18 chapters with their corresponding page numbers, covering topics like laws of motion, work and energy, electricity, plants, ecosystems, light, and more. The document also provides some sample text from the first chapter on laws of motion, which discusses concepts like displacement, distance, speed, velocity, uniform and non-uniform motion, and acceleration. Examples are given to illustrate these concepts.
The document summarizes Newton's three laws of motion:
1. The First Law states that objects at rest stay at rest and objects in motion stay in motion with constant velocity unless acted upon by a net external force. Common examples are given to illustrate this law.
2. The Second Law states that acceleration is produced when a net force acts on an object and has a magnitude directly proportional to the net force and inversely proportional to the object's mass.
3. The Third Law states that in every interaction, there is a pair of forces acting on the two interacting objects. The forces are equal in magnitude and opposite in direction.
this ppt is based on the physics chapter: force and pressure.
you can also see the other chapters on youtube
https://www.youtube.com/watch?v=nejarAzn76A
This document is a chapter about motion and speed that includes definitions of key vocabulary words and explanations of concepts. It defines motion as a change in position, and position as the location of an object. Distance is defined as how far an object is from one position to another, and is measured using a ruler or tape measure. Speed is the distance an object moves over a certain amount of time, and is calculated as speed equals distance divided by time. Faster moving objects cover more distance in a shorter time compared to slower moving objects. Maps are used to show the positions of objects and use directions like north, south, east and west to help readers understand locations.
This is a unified melc-based powerpoint presentation in Science 7. If you want to avail the powerpoint please contact me on my facebook account: Jady Claire Jackson Lullegao
Speed is defined as the ratio of distance to time taken, and is a measure of how fast an object is moving. It is commonly used to describe how long it will take to travel between places instead of providing exact distances. To calculate speed, the total distance traveled is divided by the total time taken, while instantaneous speed is the speed measured at a particular moment. Speed can help determine the rate of motion and is often expressed in units such as meters per second.
A leopard must be able to change its speed and direction quickly to catch prey. Motion involves an object changing position relative to a reference point over time. Speed is the distance traveled divided by the time taken and is measured in meters per second. Average speed is the total distance divided by the total time, while instantaneous speed is an object's speed at a particular moment. Students can calculate their own speed by timing themselves walking between two points and measuring the distance.
This document provides definitions and explanations of key concepts related to motion, including:
1. Motion is defined as a change in an object's position over time, while rest is defined as no change in position over time. Motion and rest are relative terms depending on the frame of reference.
2. Distance is the total path length traveled by an object, while displacement is the straight-line distance between the starting and ending points of an object's motion. Displacement is a vector quantity.
3. Speed is defined as the rate of change of distance over time and is a scalar quantity. Velocity is defined as the rate of change of displacement over time and includes both magnitude and direction, making it a vector quantity
G7 Science Q3- Week 1_2- Force and Motion Standards.pptNhiceElardoTelen
1) The document discusses force and motion standards related to determining the relationship between velocity and acceleration, and the effect of balanced and unbalanced forces on an object.
2) It defines key terms related to motion including distance, displacement, speed, velocity, and acceleration. Distance refers to how far an object travels regardless of direction, while displacement takes direction into account. Speed is how fast something moves, while velocity includes both speed and direction.
3) Acceleration is defined as the rate of change of velocity, whether that be a change in speed, direction, or both. Equations for calculating speed, velocity and acceleration from distance, time and other variables are provided.
1. The student was asked to grow an uncontaminated culture of microbes. The method provided involved sterilizing equipment, heating an inoculating loop, spreading bacteria onto agar jelly in a petri dish, and incubating the dish at 25°C.
2. The student tested the effectiveness of four antibiotic solutions by placing sterile paper discs dipped in each solution onto agar with growing bacteria. After two days of incubation, different sized regions with no bacterial growth were observed around each disc.
3. The least effective antibiotic produced the smallest region without bacteria, as the size of this region indicates how strongly the antibiotic inhibited bacterial growth. Calculations of the area of the bacterial-free zones would be inaccurate
Methicillin-resistant Staphylococcus aureus (MRSA) is a bacterium that causes difficult-to-treat infections in humans. MRSA developed from a similar strain called Methicillin-sensitive Staphylococcus aureus (MSSA) that was treatable with antibiotics. Through natural selection, some MSSA bacteria gained mutations that made them resistant to antibiotics. Those resistant bacteria survived exposure to antibiotics and passed on the resistance genes through asexual reproduction, leading to the emergence of the MRSA strain.
The document discusses antibiotic resistance, specifically Methicillin-resistant Staphylococcus aureus (MRSA). MRSA infections are difficult to treat with antibiotics that previously worked. This is because MRSA developed from a strain called Methicillin-sensitive Staphylococcus aureus that was susceptible to antibiotics, through natural selection whereby bacteria resistant to antibiotics survived and passed on those resistance genes. New treatments are needed to kill MRSA since existing antibiotics are no longer effective.
The document summarizes data from a hospital in the 1800s that showed higher death rates for women giving birth in Ward A compared to Ward B. After 1840, only doctors worked in Ward A while only midwives worked in Ward B, resulting in a much lower death rate in Ward B. In 1847, Semmelweis required doctors to wash their hands with chloride of lime before childbirth. This led to a significant reduction in the Ward A death rate in 1848-1849, bringing it closer to the rate in Ward B. The hand washing killed bacteria that doctors were transmitting from autopsies to women during childbirth.
This document discusses motion and how it is described. It explains that motion can be linear, circular, rotational, or vibrational. Linear motion along a straight line is the simplest to describe. Position is described relative to a reference point, while displacement is the straight-line distance between the initial and final positions. Distance refers to the total path length traveled, which can be different from displacement. Uniform motion means equal distances are covered in equal time intervals, while non-uniform motion means unequal distances are covered. Speed is the distance traveled per unit time and gives only the rate of motion, while velocity also considers direction of motion. Average speed and velocity can be used to describe non-uniform motion.
Straight Motion Regular Report by Fildia PutriIndy Puteri
The document describes an experiment on straight line motion. The purpose was to understand the difference between distance and displacement, determine speed and average speed, and investigate the relationship between displacement and time for objects moving in a straight line with constant speed. Students measured the distance, displacement, and travel time of three objects moving along three different tracks using a meter and stopwatch. Data was also collected for a bubble rising in a vertical glass tube at different distances, measuring the travel time. The results showed that objects with higher speeds took less time to travel the same distance, and objects placed higher in the tube moved faster between points.
This document discusses motion, speed, and time. It defines motion as a change in an object's position and speed as the distance covered by an object per unit of time. Uniform motion has constant speed while non-uniform motion has changing speed. Time is measured using periodic events like the sun's motion or a pendulum's oscillations. A simple pendulum's time period is the time taken to complete one oscillation. Distance and time graphs can represent motion, with uniform motion shown as a straight line.
The document summarizes some key aspects of Einstein's Special Theory of Relativity in an entertaining way. It explains that (1) nothing can travel faster than the speed of light, which is constant for all observers; (2) as objects approach the speed of light, time slows down, length contracts, and mass increases to account for the constant speed of light; and (3) these effects have been observed in particle accelerators where particles swell in mass as they near the speed of light.
1) The document discusses Newton's laws of motion and concepts related to motion including velocity, acceleration, uniform and non-uniform motion.
2) It defines key terms like displacement, distance, speed, velocity, uniform and non-uniform acceleration.
3) Newton's laws of motion are summarized - including that a body at rest stays at rest and a body in motion stays in motion unless acted on by a force, and that acceleration is directly proportional to force.
This document defines and explains key concepts related to motion, including:
- Motion is defined as a change in position over time. A point of reference is used to measure an object's changing position.
- Displacement refers to the straight line distance and direction between two positions, while distance is the total path traveled.
- Speed is defined as distance divided by time and can be measured in units like km/h or m/s. Speed with direction is called velocity.
- Instantaneous speed is an object's speed at a moment in time, which may vary, while average speed represents the speed over the entire journey. Constant speed means the instantaneous speed does not change.
- A
The document discusses motion and force, covering distance, time, speed, and forces. Chapter Twelve focuses on distance, time, and speed, defining key terms like speed, velocity, constant velocity, and average speed. It explains how scientists describe motion using measurements of distance, time, and speed, and how these values are related through equations.
The document discusses various concepts related to motion including:
1. Motion is defined as the change in position of a body with time. It can be described by distance travelled and displacement. Displacement refers to the shortest distance between initial and final positions along with direction, while distance travelled is the actual path length.
2. Uniform and non-uniform motion are defined based on whether equal distances are travelled in equal time intervals. Distance-time and velocity-time graphs are used to represent motion.
3. Key concepts like speed, average speed, velocity, average velocity, acceleration, uniform and non-uniform acceleration, retardation, and equations of motion relating these quantities are explained.
4. Circular
This document provides an overview of the module on the laws of motion. [1] It will cover description of motion, causes of motion, and forces and equilibrium. [2] Students will learn about concepts like distance, displacement, speed, velocity, uniform velocity, uniform acceleration, inertia, and Newton's laws of motion. [3] They will complete activities to explore these concepts hands-on and apply their understanding.
This document contains a table of contents for a science textbook. It lists 18 chapters with their corresponding page numbers, covering topics like laws of motion, work and energy, electricity, plants, ecosystems, light, and more. The document also provides some sample text from the first chapter on laws of motion, which discusses concepts like displacement, distance, speed, velocity, uniform and non-uniform motion, and acceleration. Examples are given to illustrate these concepts.
The document summarizes Newton's three laws of motion:
1. The First Law states that objects at rest stay at rest and objects in motion stay in motion with constant velocity unless acted upon by a net external force. Common examples are given to illustrate this law.
2. The Second Law states that acceleration is produced when a net force acts on an object and has a magnitude directly proportional to the net force and inversely proportional to the object's mass.
3. The Third Law states that in every interaction, there is a pair of forces acting on the two interacting objects. The forces are equal in magnitude and opposite in direction.
this ppt is based on the physics chapter: force and pressure.
you can also see the other chapters on youtube
https://www.youtube.com/watch?v=nejarAzn76A
This document is a chapter about motion and speed that includes definitions of key vocabulary words and explanations of concepts. It defines motion as a change in position, and position as the location of an object. Distance is defined as how far an object is from one position to another, and is measured using a ruler or tape measure. Speed is the distance an object moves over a certain amount of time, and is calculated as speed equals distance divided by time. Faster moving objects cover more distance in a shorter time compared to slower moving objects. Maps are used to show the positions of objects and use directions like north, south, east and west to help readers understand locations.
This is a unified melc-based powerpoint presentation in Science 7. If you want to avail the powerpoint please contact me on my facebook account: Jady Claire Jackson Lullegao
Speed is defined as the ratio of distance to time taken, and is a measure of how fast an object is moving. It is commonly used to describe how long it will take to travel between places instead of providing exact distances. To calculate speed, the total distance traveled is divided by the total time taken, while instantaneous speed is the speed measured at a particular moment. Speed can help determine the rate of motion and is often expressed in units such as meters per second.
A leopard must be able to change its speed and direction quickly to catch prey. Motion involves an object changing position relative to a reference point over time. Speed is the distance traveled divided by the time taken and is measured in meters per second. Average speed is the total distance divided by the total time, while instantaneous speed is an object's speed at a particular moment. Students can calculate their own speed by timing themselves walking between two points and measuring the distance.
This document provides definitions and explanations of key concepts related to motion, including:
1. Motion is defined as a change in an object's position over time, while rest is defined as no change in position over time. Motion and rest are relative terms depending on the frame of reference.
2. Distance is the total path length traveled by an object, while displacement is the straight-line distance between the starting and ending points of an object's motion. Displacement is a vector quantity.
3. Speed is defined as the rate of change of distance over time and is a scalar quantity. Velocity is defined as the rate of change of displacement over time and includes both magnitude and direction, making it a vector quantity
G7 Science Q3- Week 1_2- Force and Motion Standards.pptNhiceElardoTelen
1) The document discusses force and motion standards related to determining the relationship between velocity and acceleration, and the effect of balanced and unbalanced forces on an object.
2) It defines key terms related to motion including distance, displacement, speed, velocity, and acceleration. Distance refers to how far an object travels regardless of direction, while displacement takes direction into account. Speed is how fast something moves, while velocity includes both speed and direction.
3) Acceleration is defined as the rate of change of velocity, whether that be a change in speed, direction, or both. Equations for calculating speed, velocity and acceleration from distance, time and other variables are provided.
1. The student was asked to grow an uncontaminated culture of microbes. The method provided involved sterilizing equipment, heating an inoculating loop, spreading bacteria onto agar jelly in a petri dish, and incubating the dish at 25°C.
2. The student tested the effectiveness of four antibiotic solutions by placing sterile paper discs dipped in each solution onto agar with growing bacteria. After two days of incubation, different sized regions with no bacterial growth were observed around each disc.
3. The least effective antibiotic produced the smallest region without bacteria, as the size of this region indicates how strongly the antibiotic inhibited bacterial growth. Calculations of the area of the bacterial-free zones would be inaccurate
Methicillin-resistant Staphylococcus aureus (MRSA) is a bacterium that causes difficult-to-treat infections in humans. MRSA developed from a similar strain called Methicillin-sensitive Staphylococcus aureus (MSSA) that was treatable with antibiotics. Through natural selection, some MSSA bacteria gained mutations that made them resistant to antibiotics. Those resistant bacteria survived exposure to antibiotics and passed on the resistance genes through asexual reproduction, leading to the emergence of the MRSA strain.
The document discusses antibiotic resistance, specifically Methicillin-resistant Staphylococcus aureus (MRSA). MRSA infections are difficult to treat with antibiotics that previously worked. This is because MRSA developed from a strain called Methicillin-sensitive Staphylococcus aureus that was susceptible to antibiotics, through natural selection whereby bacteria resistant to antibiotics survived and passed on those resistance genes. New treatments are needed to kill MRSA since existing antibiotics are no longer effective.
The document summarizes data from a hospital in the 1800s that showed higher death rates for women giving birth in Ward A compared to Ward B. After 1840, only doctors worked in Ward A while only midwives worked in Ward B, resulting in a much lower death rate in Ward B. In 1847, Semmelweis required doctors to wash their hands with chloride of lime before childbirth. This led to a significant reduction in the Ward A death rate in 1848-1849, bringing it closer to the rate in Ward B. The hand washing killed bacteria that doctors were transmitting from autopsies to women during childbirth.
The document summarizes data from the 1800s that showed death rates of women giving birth in two hospital wards: Ward A and Ward B. Before 1840, both wards had similar high death rates as doctors and midwives worked in both. After 1840, Ward A had only doctors while Ward B had only midwives, and Ward B saw significantly lower death rates. Dr. Semmelweis later required doctors to wash their hands in chloride of lime solution before deliveries in Ward A, which further reduced Ward A's death rate to match Ward B's lower level.
Tuberculosis (TB) is caused by the Mycobacterium tuberculosis bacterium. When someone with TB coughs or sneezes, the bacteria are expelled into the air and can be inhaled by others. If breathed in, the bacteria initially infect the lungs. In the lungs, the bacteria can multiply and cause lesions and inflammation. Other types of microorganisms besides bacteria, such as viruses, can also cause infectious disease. When the body is exposed to TB bacteria, it mounts an immune response to fight the infection by using white blood cells, antibodies, and other mechanisms of defense.
The document discusses diet, exercise, and metabolic rate. It defines metabolic rate as the rate of chemical reactions in the body. While genes affect metabolic rate, exercise can increase it. A balanced diet with carbohydrates, proteins, and fats provides energy, builds cells, and stores energy. An imbalanced diet can lead to malnutrition by providing too much or too little energy compared to what the body needs. The document questions an advert claiming quick weight loss from a program, as it lacks long-term data and sample size details.
The document discusses diet, exercise, and weight management. It defines metabolic rate as the rate at which the body burns calories and explains that some people have naturally low metabolic rates. It recommends exercise as a way to increase metabolic rate. Diet components like carbohydrates, proteins, and fats serve important functions, and an imbalanced diet can lead to malnutrition. The document questions the validity of an advert claiming quick weight loss from a "Dropweight" program based on reported one-day results.
Tuberculosis (TB) is caused by the Mycobacterium tuberculosis bacterium. When people with TB cough or sneeze, they expel the bacteria into the air. If others breathe these bacteria in, they can become infected. The bacteria first infect the lungs or bronchioles. In the body, the bacteria produce toxins that damage cells. The body fights the infection through white blood cells that engulf and destroy bacteria and produce antibodies and antitoxins. Vaccines work by exposing the body to an inactive form of the disease-causing microbe, allowing it to develop antibodies without risk of illness. These antibodies then provide future protection against the live microbe.
1) The document is a revision checklist for additional GCSE science covering topics in physics including forces, motion, braking, terminal velocity, elasticity, energy, momentum, static electricity, electrical circuits, household electricity, current, charge, power, atomic structure, radiation, nuclear fission, and nuclear fusion.
2) It lists key terms, concepts, and formulas to define and explanations to provide for each topic.
3) The checklist provides resources for students to review physics content and ensure they understand the essential information for their GCSE exam.
This document contains a revision checklist for the GCSE Core Science P1 Physics exam. It lists several topics and subtopics that students should review in preparation for the exam, including: infrared radiation; states of matter; conduction, convection, and evaporation/condensation as methods of heat transfer; factors affecting the rate of heat transfer; solar panels; specific heat capacity; energy efficiency and Sankey diagrams; electrical appliances and calculating energy transfers; methods of generating electricity including alternative sources; the National Grid; waves including transverse/longitudinal waves, electromagnetic spectrum, reflection, refraction, and diffraction of waves; and Doppler effect and evidence for the Big Bang theory.
This document provides an overview of the content covered in additional science C2: chemistry. It outlines several key topics in chemistry including structure and bonding, atomic structure and quantitative chemistry, rates of reaction, endo/exothermic reactions, acids bases and salts, and electrolysis. For each topic, it lists the main concepts, definitions, and processes that students are expected to understand at a higher level, such as describing bonding using diagrams, calculating relative formula mass, explaining how factors affect reaction rates, writing equations for acid-base reactions, and describing electrolysis processes and products. The document serves as a revision checklist for students to ensure they have learned the essential high-level information and skills for the additional chemistry content.
This document is a revision checklist for GCSE core science covering various topics in chemistry. It provides a list of key concepts and processes to review for each topic, including fundamental chemistry ideas like atomic structure, limestone and building materials, metals and their uses, crude oil and fuels, and changes to the Earth's atmosphere. For each item, it indicates related videos, exam questions, and whether it is core or higher content.
This document provides an outline of topics covered in Additional Science B2: Biology. It includes sections on cells and transport, tissues and organ systems, photosynthesis, organisms and their environment, aerobic and anaerobic respiration, cell division and inheritance, speciation, and includes learning objectives for each section such as describing processes like diffusion, the roles of organs in the digestive system, the process of photosynthesis, and more. It also provides exam questions, activities, and checkpoints to evaluate understanding of the material.
This document provides an overview of topics covered in a biology course, including:
- The components of a balanced diet and how exercise affects health.
- How pathogens make us ill and how the body protects against them.
- The development and testing of medical drugs, and issues around drug dependence.
- Genetic variation, inheritance, and different types of reproduction.
- Evolution by natural selection and genetic variation over generations.
- Ecological concepts like food chains, nutrient cycling, and indicator species.
X-rays have a short wavelength and can cause ionization. They are used in medicine for diagnosis and treatment, but precautions must be taken when operating X-ray machines. Ultrasound uses high frequency sound waves above the human hearing range. The waves reflect off boundaries and the time of reflections can be used to determine distances between interfaces in different media. Lenses refract light to form images. A convex lens brings parallel rays to a focus at its principal focus, defined by the focal length. The nature of images depends on size, orientation, and whether real or virtual.
The document summarizes key concepts in chemistry including the periodic table, properties of groups in the periodic table, hard and soft water, chemical reactions, and organic compounds. It describes how elements are arranged in the modern periodic table by electronic structure and properties of groups such as metals, nonmetals, and halogens. It also discusses chemical tests and reactions including flame tests, precipitation reactions, acid-base titrations, and the production of ammonia via the Haber process.
This document provides information on various biology topics including:
- Diffusion and osmosis, the movement of substances through membranes. Active transport requires energy.
- Exchange surfaces are effective with large surface area, thinness, good blood supply and ventilation like in alveoli and villi.
- During breathing, the ribcage and diaphragm work to decrease thoracic pressure and draw air into the lungs. Artificial aids can help breathing.
- In plants, carbon dioxide enters leaves and water and minerals are absorbed by roots, transported by xylem and phloem.
- The heart has four chambers and pumps blood through two circulation systems. Blood flows through arteries, veins
The document discusses key economic concepts related to government objectives and the functioning of the economy. It covers topics such as different types of economies, market failures including externalities and public goods, the economic cycle, fiscal and monetary policies, and the role of the EU. The key points are that candidates should understand the principal objectives of governments in terms of economic growth, employment, prices and trade balances. They should also be aware of how markets can fail to allocate resources efficiently and the roles of government and central banks in addressing these issues.
The document outlines a specification for teaching personal finance concepts. It covers understanding the personal lifecycle and how needs and wants change throughout different stages of life. Students will learn to make financial decisions by weighing costs and benefits and considering opportunity costs. They will also explore concepts related to spending, saving, borrowing money, and managing personal finances. The specification also addresses topics related to work, including rewards, labor markets, unemployment, and the impact of globalization. Finally, it covers understanding international trade, exchange rates, and the influence of consumers on national and global economies.
1. 13 Motion and Time
I
n Class VI, you learnt about different 13.1 SLOW OR FAST
types of motions. You learnt that a We know that some vehicles move faster
motion could be along a straight line, than others. Even the same vehicle may
it could be circular or periodic. Can you move faster or slower at different times.
recall these three types of motions? Make a list of ten objects moving along
Table 13.1 gives some common a straight path. Group the motion of
examples of motions. Identify the type these objects as slow and fast. How did
of motion in each case. you decide which object is moving slow
Table 13.1 Some examples of and which one is moving fast.
different types of motion If vehicles are moving on a road in
Example of Type of motion the same direction, we can easily tell
which one of them is moving faster than
motion Along a straight
line/circular/ the other.
periodic Activity 13.1
Soldiers in a
Look at Fig. 13.1. It shows the position
march past
of some vehicles moving on a road in
Bullock cart the same direction at some instant of
moving on a time. Now look at Fig. 13.2. It shows the
straight road position of the same vehicles after some
Hands of an time. From your observation of the two
athlete in a race figures, answer the following questions:
Pedal of a bicycle Which vehicle is moving the fastest
in motion of all? Which one of them is moving the
Motion of the earth slowest of all?
around the sun
The distance moved by objects in a
given interval of time can help us to
Motion of a swing
decide which one is faster or slower. For
Motion of a example, imagine that you have gone to
pendulum see off your friend at the bus stand.
It is common experience that the Suppose you start pedalling your bicycle
motion of some objects is slow while that at the same time as the bus begins to
of some others is fast. move. The distance covered by you after
2. it is easy to decide whose speed
is the highest. One who takes
shortest time to cover the
distance of 100 metres has the
highest speed.
13.2 SPEED
You are probably familiar with
the word speed. In the
examples given above, a higher
speed seems to indicate that a
given distance has been
covered in a shorter time, or a
larger distance covered in a
given time.
Fig. 13.1 Vehicles moving in the same The most convenient way to
direction on a road find out which of the two or
more objects is moving faster
is to compare the distances
moved by them in a unit time.
Thus, if we know the distance
covered by two buses in one
hour, we can tell which one is
slower. We call the distance
covered by an object in a unit
time as the speed of the object.
When we say that a car is
moving with a speed of 50
kilometres per hour, it implies
that it will cover a distance of
Fig. 13.2 Position of vehicles shown in 50 kilometres in one hour. However, a
Fig. 13.1 after some time car seldom moves with a constant speed
for one hour. In fact, it starts moving
5 minutes would be much smaller than slowly and then picks up speed. So,
that covered by the bus. Would you say when we say that the car has a speed of
that the bus is moving faster than the 50 kilometres per hour, we usually
bicycle? consider only the total distance covered
We often say that the faster vehicle by it in one hour. We do not bother
has a higher speed. In a 100-metre race whether the car has been moving with
144 SCIENCE
3. a constant speed or not during that they found that the sun rises everyday
hour. The speed calculated here is in the morning. The time between one
actually the average speed of the car. In sunrise and the next was called a day.
this book we shall use the term speed Similarly, a month was measured from
for average speed So, for us the speed
speed. one new moon to the next. A year was
is the total distance covered divided fixed as the time taken by the earth to
by the total time taken. Thus,
taken complete one revolution of the sun.
Total distance covered Often we need to measure intervals
Speed =
Total time taken of time which are much shorter than a
In everyday life we seldom find objects day. Clocks or watches are perhaps the
moving with a constant speed over long most common time measuring devices.
distances or for long durations of time. Have you ever wondered how clocks and
If the speed of an object moving along watches measure time?
a straight line keeps changing, its The working of clocks is rather
motion is said to be non-uniform On
non-uniform. complex. But all of them make use of
the other hand, an object moving along some periodic motion. One of the most
a straight line with a constant speed well-known periodic motions is that of
is said to be in uniform motion In
motion. a simple pendulum
pendulum.
this case, the average speed is the
same as the actual speed.
We can determine the speed of a given
object once we can measure the time
taken by it to cover a certain distance.
In Class VI you learnt how to measure
distances. But, how do we measure
time? Let us find out.
13.3 MEASUREMENT OF TIME
If you did not have a clock, how would (b) Table clock
(a) Wall clock
you decide what time of the day it is?
Have you ever wondered how our elders
could tell the approximate time of the
day by just looking at shadows?
How do we measure time interval of
a month? A year?
Our ancestors noticed that many
events in nature repeat themselves after (c) Digital clock
definite intervals of time. For example, Fig. 13.3 Some common clocks
M OTION AND TIME 145
4. to A, to B and back to O. The
pendulum also completes one
oscillation when its bob moves
from one extreme position A to the
other extreme position B and
comes back to A. The time taken
by the pendulum to complete one
oscillation is called its time
period.
period
Activity 13.2
Set up a simple pendulum as
shown in Fig. 13.4 (a) with a
thread or string of length nearly
one metre. Switch off any fans
nearby. Let the bob of the
pendulum come to rest at its
A
B mean position. Mark the mean
O
position of the bob on the floor
below it or on the wall behind it.
Fig. 13.4 (a) A simple Fig. 13.4 (b) Different To measure the time period of
pendulum positions of the bob of an
oscillating simple pendulum
the pendulum we will need
a stopwatch. However, if a
A simple pendulum consists of a stopwatch is not available, a table
small metallic ball or a piece of stone clock or a wristwatch can be used.
suspended from a rigid stand by a To set the pendulum in motion,
thread [Fig. 13.4 (a)]. The metallic ball gently hold the bob and move it slightly
is called the bob of the pendulum. to one side. Make sure that the string
Fig. 13.4 (a) shows the pendulum at attached to the bob is taut while you
rest in its mean position. When the bob displace it. Now release the bob from its
of the pendulum is released after taking displaced position. Remember that the
it slightly to one side, it begins to move bob is not to be pushed when it is
to and fro [Fig. 13.4 (b)]. The to and fro released. Note the time on the clock
motion of a simple pendulum is an when the bob is at its mean position.
example of a periodic or an oscillatory Instead of the mean position you may
motion. note the time when the bob is at one of
The pendulum is said to have its extreme positions. Measure the time
completed one oscillation when its bob, the pendulum takes to complete 20
starting from its mean position O, moves oscillations. Record your observations
146 SCIENCE
5. in Table 13.2. The first observation cells. These clocks are called quartz
shown is just a sample. Your clocks. The time measured by quartz
observations could be different from clocks is much more accurate than that
this. Repeat this activity a few times and by the clocks available earlier.
record your observations. By dividing
Units of time and speed
the time taken for 20 oscillations by 20,
The basic unit of time is a second Its
second.
get the time taken for one oscillation, or
symbol is s. Larger units of time are
the time period of the pendulum.
minutes (min) and hours (h). You
Is the time period of your pendulum
already know how these units are related
nearly the same in all cases?
to one another.
Note that a slight change in the initial
What would be the basic unit of
displacement does not affect the time
speed?
period of your pendulum.
Since the speed is distance/time, the
Nowadays most clocks or watches
basic unit of speed is m/s. Of course, it
have an electric circuit with one or more
could also be expressed in other units
Table 13.2 Time period of a simple such as m/min or km/h.
pendulum
You must remember that the
Length of the string = 100 cm symbols of all units are written in
S.No. Time taken for 20 Time period singular.
singular For example, we write 50 km
oscillations and not 50 kms, or 8 cm and not 8 cms.
1. 42 s 2.1 s Boojho is wondering how many
seconds there are in a day and how
2.
many hours in a year. Can you help
3. him?
There is an interesting story about the discovery that the time period of a given
pendulum is constant. You might have heard the name of famous scientist
Galileo Galilie (A.D. 1564 –1642). It is said that once Galileo was sitting in a
church. He noticed that a lamp suspended from the ceiling with a chain was
moving slowly from one side to the other. He was surprised to find that his
pulse beat the same number of times during the interval in which the lamp
completed one oscillation. Galileo experimented with various pendulums to
verify his observation. He found that a pendulum of a given length takes always
the same time to complete one oscillation. This observation led to the
development of pendulum clocks. Winding clocks and wristwatches were
refinements of the pendulum clocks.
M OTION AND TIME 147
6. Different units of time are used Many time measuring devices were
depending on the need. For example, it used in different parts of the world before
is convenient to express your age in the pendulum clocks became popular.
years rather than in days or hours. Sundials, water clocks and sand clocks
Similarly, it will not be wise to express are some examples of such devices.
in years the time taken by you to cover Different designs of these devices were
the distance between your home and developed in different parts of the world
your school. (Fig. 13.5).
How small or large is a time interval
13.4 MEASURING SPEED
of one second? The time taken in saying
Having learnt how to measure time and
aloud “two thousand and one” is nearby
distance, you can calculate the speed of
one second. Verify it by counting aloud
an object. Let us find the speed of a ball
from "two thousand and one" to "two
moving along the ground.
thousand and ten". The pulse of a
normal healthy adult at rest beats about Activity 13.3
72 times in a minute that is about 12
Draw a straight line on the ground with
times in 10 seconds. This rate may be
chalk powder or lime and ask one of
slightly higher for children.
your friends to stand 1 to 2 m away from
it. Let your friend gently roll a ball along
the ground in a direction perpendicular
Paheli wondered how time was to the line. Note the time at the moment
measured when pendulum the ball crosses the line and also when
clocks were not available. it comes to rest (Fig. 13.6). How much
time does the ball take to come to rest?
The smallest time interval that can be measured with commonly available
clocks and watches is one second. However, now special clocks are available
that can measure time intervals smaller than a second. Some of these clocks
can measure time intervals as small as one millionth or even one billionth of a
second. You might have heard the terms like microsecond and nanosecond.
One microsecond is one millionth of a second. A nanosecond is one billionth
of a second. Clocks that measure such small time intervals are used for scientific
research. The time measuring devices used in sports can measure time intervals
that are one tenth or one hundredth of a second. On the other hand, times of
historical events are stated in terms of centuries or millenniums. The ages of
stars and planet are often expressed in billions of years. Can you imagine the
range of time intervals that we have to deal with?
148 SCIENCE
7. (b) Sand clock
(a) Sundial at Jantar Mantar, Delhi (c) Water clock
Fig. 13.5 Some ancient time-measuring devices
Measure the distance between the point
at which the ball crosses the line and
the point where it comes to rest. You
can use a scale or a measuring
tape. Let different groups repeat the
activity. Record the measurements in
Table 13.3. In each case calculate the
speed of the ball.
You may now like to compare your
speed of walking or cycling with that of
your friends. You need to know the
distance of the school from your home
or from some other point. Each one of
you can then measure the time taken
to cover that distance and calculate your
speed. It may be interesting to know who
amongst you is the fastest. Speeds of
Fig. 13.6 Measuring the speed of a ball some living organisms are given in
M OTION AND TIME 149
8. Table 13.3 Distance moved and time taken by a moving ball
Name of the group Distance moved by Time taken (s) Speed = Distance/
the ball (m) T ime taken (m/s)
Table 13.4, in km/h. You can calculate Time taken = Distance/Speed
the speeds in m/s yourself.
Rockets, launching satellites into
earth’s orbit, often attain speeds up to
Boojho wants to know
8 km/s. On the other hand, a tortoise
whether there is any device
can move only with a speed of about 8
that measures the speed.
cm/s. Can you calculate how fast is the
rocket compared with the tortoise?
Once you know the speed of an You might have seen a meter fitted
object, you can find the distance moved on top of a scooter or a motorcycle.
by it in a given time. All you have to do Similarly, meters can be seen on the
is to multiply the speed by time. Thus, dashboards of cars, buses and other
Distance covered = Speed Time vehicles. Fig. 13.7 shows the dashboard
You can also find the time an object of a car. Note that one of the meters has
would take to cover a distance while km/h written at one corner. This is
moving with a given speed. called a speedometer It records the
speedometer.
Table 13.4 Fastest speed that some animals can attain
S. No. Name of the object Speed in km/h Speed in m/s
320 10 0 0
1. Falcon 320
60 60
2. Cheetah 112
3. Blue fish 40 – 46
4. Rabbit 56
5. Squirrel 19
6. Domestic mouse 11
7. Human 40
8. Giant tortoise 0.27
9. Snail 0.05
150 SCIENCE
9. 13.5 DISTANCE-TIME GRAPH
You might have seen that newspapers,
magazines, etc., present information in
various forms of graphs to make it
Table 13.5 Odometer reading at
different times of the journey
Time Odometer Distance from
(AM) reading the starting
point
8:00 AM 36540 km 0 km
8:30 AM 36560 km 20 km
9:00 AM 36580 km 40 km
9:30 AM 36600 km 60 km
Fig. 13.7 The dashboard of a car 10:00 AM 36620 km 80 km
speed directly in km/h. There is also
another meter that measures the
distance moved by the vehicle. This
meter is known as an odometer
odometer.
While going for a school picnic, Paheli
decided to note the reading on the
odometer of the bus after every
30 minutes till the end of the journey.
Later on she recorded her readings in
Table 13.5.
Can you tell how far was the picnic Fig. 13.8 A bar graph showing runs scored by
spot from the school? Can you calculate a team in each over
the speed of the bus? Looking at the
Table, Boojho teased Paheli whether she interesting. The type of graph shown in
can tell how far they would have Fig. 13.8 is known as a bar graph.
travelled till 9:45 AM. Paheli had no Another type of graphical representation
answer to this question. They went to is a pie chart (Fig. 13.9). The graph
their teacher. She told them that one shown in Fig. 13.10 is an example of a
way to solve this problem is to plot a line graph. The distance-time graph is a
distance-time graph. Let us find out how line graph. Let us learn to make such a
such a graph is plotted. graph.
M OTION AND TIME 151
10. Oxygen Other gases Y
X O X
Nitrogen
Fig. 13.9 A pie chart showing composition
Y
of air
Y Fig. 13.11 x-axis and y-axis on a graph paper
80
70 Therefore, we shall use only the shaded
60
part of the graph shown in Fig. 13.11.
50
Weight (in kg)
40
Boojho and Paheli found out the
30 distance travelled by a car and the time
20 taken by it to cover that distance. Their
10 data is shown in Table 13.6.
X
2 4 6 8 10 12 14 16 18 20 22
Table 13.6 The motion of a car
Age (in year)
S. No. Time Distance
Fig. 13.10 A line graph showing change in
weight of a man with age 1. 0 0
2. 1 min 1 km
Take a sheet of graph paper. Draw
two lines perpendicular to each other 3. 2 min 2 km
on it, as shown in Fig. 13.11. Mark the 4. 3 min 3 km
horizontal line as XOX'. It is known as
5. 4 min 4 km
the x-axis. Similarly mark the vertical
line YOY'. It is called the y-axis. The point 6. 5 min 5 km
of intersection of XOX' and YOY ' is
known as the origin O. The two You can make the graph by following
quantities between which the graph is the steps given below:
drawn are shown along these two axes. Draw two perpendicular lines to
We show the positive values on the represent the two axes and mark
x-axis along OX. Similarly, positive them as OX and OY as in Fig. 13.11.
values on the y-axis are shown along Decide the quantity to be shown
OY. In this chapter we shall consider along the x-axis and that to be
only the positive values of quantities. shown along the y-axis. In this case
152 SCIENCE
11. we show the time along the x-axis Y
and the distance along the y-axis.
Choose a scale to represent the
distance and another to represent
the time on the graph. For the motion
of the car scales could be
Time: 1 min = 1 cm
Distance: 1 km = 1 cm
Mark values for the time and the O
X
distance on the respective axes
according to the scale you have
chosen. For the motion of the car Fig. 13.12 Making a graph
mark the time 1 min, 2 min, … on
Y
the x-axis from the origin O.
Similarly, mark the distance 1 km,
2 km … on the y-axis (Fig. 13.12).
Now you have to mark the points on
the graph paper to represent each
set of values for distance and time.
Observation recorded at S. No. 1
in Table 13.6 shows that at time
0 min the distance moved is also O
X
zero. The point corresponding to this
set of values on the graph will
therefore be the origin itself. After 1 Fig. 13.13 Making a graph
minute, the car has moved a distance
of 1 km. To mark this set of values Fig. 13.13 shows the set of points on
look for the point that represents the graph corresponding to positions
1 minute on the x-axis. Draw a line of the car at various times.
parallel to the y-axis at this point. Join all the points on the graph as
Then draw a line parallel to the shown in Fig. 13.13. It is a straight
x-axis from the point corresponding line. This is the distance-time graph
to distance 1 km on the y-axis. The for the motion of the car.
point where these two lines If the distance-time graph is a
intersect represents this set of values straight line, it indicates that the
on the graph (Fig. 13.12). Similarly, object is moving with a constant
mark on the graph paper the speed. However, if the speed of the
points corresponding to different object keeps changing, the graph can
sets of values. be of any shape.
M OTION AND TIME 153
12. Y
X
Fig. 13.14 Distance-time graph of the bus
Generally, the choice of scales is not the difference between the highest
as simple as in the example given above. and the lowest values of each
We may have to choose two different scales quantity.
to represent the desired quantities on the the intermediate values of each
x-axis and the y-axis. Let us try to quantity, so that with the scale
understand this process with an example. chosen it is convenient to mark the
Let us again consider the motion of values on the graph, and
the bus that took Paheli and her friends to utilise the maximum part of the
to the picnic. The distance covered and paper on which the graph is to be
time taken by the bus are shown in drawn.
Table 13.5. The total distance covered Suppose that we have a graph paper
by the bus is 80 km. If we decide to of size 25 cm 25 cm. One of the scales
choose a scale 1 km = 1 cm, we shall which meets the above conditions and
have to draw an axis of length 80 cm. can accommodate the data of Table 13.5
This is not possible on a sheet of paper. could be
On the other hand, a scale 10 km = 1 Distance: 5 km = 1 cm, and
cm would require an axis of length only Time: 6 min = 1 cm
8 cm. This scale is quite convenient. Can you now draw the distance-time
However, the graph may cover only a graph for the motion of the bus? Is the
small part of the graph paper. Some of graph drawn by you similar to that
the points to be kept in mind while shown in Fig. 13.13?
choosing the most suitable scale for Distance-time graphs provide a
drawing a graph are: variety of information about the motion
154 SCIENCE
13. when compared to the data presented point A. We then mark the point, T, on
by a table. For example, Table 13.5 gives the graph at which this perpendicular
information about the distance moved line intersects it (Fig. 13.14). Next, we
by the bus only at some definite time draw a line through the point T parallel
intervals. On the other hand, from the to the x-axis. This intersects the y-axis
distance-time graph we can find the at the point B. The distance
distance moved by the bus at any corresponding to the point B on the
instant of time. Suppose we want to y-axis, OB, gives us the distance in km
know how much distance the bus had covered by the bus at 8:15 AM. How muc
travelled at 8:15 AM. We mark the point is this distance in km? Can you now
corresponding to the time (8:15 AM) on help Paheli to find the distance moved
the x-axis. Suppose this point is A. Next by the bus at 9:45 AM? Can you also
we draw a line perpendicular to the find the speed of the bus from its
x-axis (or parallel to the y-axis) at distance-time graph?
Keywords
Bar graph Oscillation Time period
Graphs Simple pendulum Uniform motion
Non-uniform motion Speed Unit of time
What you have Learnt
The distance moved by an object in a unit time is called its speed.
Speed of objects help us to decide which one is moving faster than the
other.
The speed of an object is the distance travelled divided by the time taken
to cover that distance. Its basic unit is metre per second (m/s).
Periodic events are used for the measurement of time. Periodic motion of
a pendulum has been used to make clocks and watches.
Motion of objects can be presented in pictorial form by their
distance-time graphs.
The distance-time graph for the motion of an object moving with a constant
speed is a straight line.
M OTION AND TIME 155
14. Exercises
1. Classify the following as motion along a straight line, circular or
oscillatory motion:
(i) Motion of your hands while running.
(ii) Motion of a horse pulling a cart on a straight road.
(iii) Motion of a child in a merry-go-round.
(iv) Motion of a child on a see-saw.
(v) Motion of the hammer of an electric bell.
(vi) Motion of a train on a straight bridge.
2. Which of the following are not correct?
(i) The basic unit of time is second.
(ii) Every object moves with a constant speed.
(iii) Distances between two cities are measured in kilometres.
(iv) The time period of a given pendulum is not constant.
(v) The speed of a train is expressed in m/h.
3. A simple pendulum takes 32 s to complete 20 oscillations. What is the
time period of the pendulum?
4. The distance between two stations is 240 km. A train takes 4 hours to
cover this distance. Calculate the speed of the train.
5. The odometer of a car reads 57321.0 km when the clock shows the time
08:30 AM. What is the distance moved by the car, if at 08:50 AM, the
odometer reading has changed to 57336.0 km? Calculate the speed of
the car in km/min during this time. Express the speed in km/h also.
6. Salma takes 15 minutes from her house to reach her school on a
bicycle. If the bicycle has a speed of 2 m/s, calculate the distance
between her house and the school.
7. Show the shape of the distance-time graph for the motion in the
following cases:
(i) A car moving with a constant speed.
(ii) A car parked on a side road.
8. Which of the following relations is correct?
Distance
(i) Speed = Distance Time (ii) Speed =
Time
Time 1
(iii) Speed = (iv) Speed =
Distance Distance Time
156 SCIENCE
15. 9. The basic unit of speed is:
(i) km/min (ii) m/min
(iii) km/h (iv) m/s
10. A car moves with a speed of 40 km/h for 15 minutes and then with a
speed of 60 km/h for the next 15 minutes. The total distance covered by
the car is:
(i) 100 km (ii) 25 km
(iii) 15 km (iv) 10 km
11. Suppose the two photographs, shown in Fig. 13.1 and Fig. 13.2, had
been taken at an interval of 10 seconds. If a distance of 100 metres is
shown by 1 cm in these photographs, calculate the speed of the blue car.
12. Fig. 13.15 shows the distance-time graph for the motion of two vehicles A
and B. Which one of them is moving faster?
Fig. 13.15 Distance-time graph for the motion of two cars
13. Which of the following distance-time graphs shows a truck moving with
speed which is not constant?
(i) (ii)
M OTION AND TIME 157
16. Extend Learning — Activities and (iv)
(iii) Projects
1. You can make your own sundial and use it to mark the time of the day at
your place. First of all find the latitude of your city with the help of an
atlas. Cut out a triangular piece of a cardboard such that its one angle
is equal to the latitude of your place and the angle opposite to it is a
right angle. Fix this piece, called gnomon vertically along a diameter of
gnomon,
a circular board a shown in Fig. 13.16. One way to fix the gnomon could
be to make a groove along a diameter on the circular board.
Next, select an open space, which receives sunlight for most of the day.
Mark a line on the ground along the North-South direction. Place the
sundial in the sun as shown in Fig. 13.16. Mark the position of the tip
of the shadow of the gnomon on the circular board as early in the day
as possible, say 8:00 AM. Mark the position of the tip of the shadow
every hour throughout the day. Draw lines to connect each point marked
by you with the centre of the base of the gnomon as shown in Fig. 13.16.
Extend the lines on the circular board up to its periphery. You can use
this sundial to read the time of the day at your place. Remember that
the gnomon should always be placed in the North-South direction as
shown in Fig. 13.16.
2. Collect information about time-measuring devices that were used in the
Fig. 13.16
158 SCIENCE
17. ancient times in different parts of the world. Prepare a brief write up on
each one of them. The write up may include the name of the device, the
place of its origin, the period when it was used, the unit in which the time
was measured by it and a drawing or a photograph of the device, if
available.
3. Make a model of a sand clock which can measure a time interval of 2
minutes (Fig. 13.17).
Fig. 13.17
4. You can perform an interesting activity when you visit a park to ride a
swing. You will require a watch. Make the swing oscillate without
anyone sitting on it. Find its time period in the same way as you did for
the pendulum. Make sure that there are no jerks in the motion of the
swing. Ask one of your friends to sit on the swing. Push
it once and let it swing naturally. Again measure its time period.
Repeat the activity with different persons sitting on the swing. Compare
the time period of the swing measured in different cases. What
conclusions do you draw from this activity?
Did you know?
The time-keeping services in India are provided by the National Physical
Laboratory, New Delhi. The clock they use can measure time intervals
with an accuracy of one-millionth of a second. The most accurate clock
in the world has been developed by the National Institute of Standards
and Technology in the U.S.A. This clock will lose or gain one second after
running for 20 million years.
M OTION AND TIME 159