Chapter 1: Introduction to Physics Form 4 1 Physics Next > The study of matter
Objectives: ( what you will learn ) 1) understand Physics 2) base quantities & derived quantities 3) scalar quantities & vector quantities 4) measurements , using instruments 5) processes in scientific investigations Physics: Chapter 1 2 < Back Next >
Understanding Physics: Physics 3 1. “Physics” derives from Latin, “ physica” - the science of natural things; until 19 th century, it was called “ natural philosophy ”. Through its subfield of astronomy , it may be the oldest academic discipline. 2. Physics is a branch of Science for study of natural phenomena , which involves force, matter & energy; based on experimental observations & quantitative measurements. < Back Next >
Base Quantities Physical Quantities 4 Quantities that cannot be defined in any other physical quantity. < Back Next > Ampere Kelvin second kilogram meter SI Unit Current Temperature Time Mass Length Base Quantity A I K T s t kg m m l Symbol Symbol
Derived Quantities 5 Physical Quantities Quantities derived from base quantities (through mathematical combinations). Volume = Length x Breath x Height = m 3 Density = Mass ÷ Volume = kg m -3 Velocity = Displacement ÷ Time = m s -1 Acceleration = Velocity ÷ Time = m s -2 Force = Mass x Acceleration = kg m s -2 < Back Next >
6 Physical Quantities Scalar Quantity Physical quantity which has magnitude only, such as distance and mass. ( Compare them to base quantities .) Vector Quantity Physical quantity which has both magnitude and direction , such as force and pressure. ( Compare them to derived quantities .) < Back Next >
7 Physical Quantities Prefixes Simplifies description of physical quantities that are either very big or very small without losing data. < Back Next > c m µ n p symbol centi milli micro nana pico prefix 10 -2 10 -3 10 -6 10 -9 10 -12 value 10 3 k kilo 10 6 M mega 10 9 G giga T symbol tera prefix 10 12 value 1 Small quantities Big quantities
8 Physical Quantities Scientific Notation The standard form for numerical magnitude. Q x 10 n where 1 ≤ Q < 10 and n is an integer Examples : 0.000000696 m = 6.96 x 10 -7 m 911 000 000 kg = 9.11 x 10 8 kg < Back Next >
9 Measurements Accuracy measures how close a hit is to the target. If it is too far from the target, it is not accurate. Consistency measures how close together a group of hits is to the average value. If they are far apart from each other, they are not consistent. We want results that are both accurate & consistent. < Back Next > Consistent, less accurate Accurate, less consistent Not accurate, not consistent Accurate & consistent
10 Measuring Instruments Sensitivity = how small a change in reading that can be measured by an instrument < Back Next > Ruler Low, 1 mm Vernier caliper Medium, 0.1 mm Micrometer screw gauge High, 0.01 mm
11 Measurement Errors <ul><li>Incorrect calibration of instruments </li></ul>Systematic Error Occurs in one direction only. <ul><li>Zero error – pointer of instrument does not return to zero when not in use, such as a ruler worn out at one end </li></ul><ul><li>Repeated error in reaction time </li></ul><ul><li>Wrong assumption </li></ul>too low too high Always negative Always positive May arise from various causes. or < Back Next >
12 Measurement Errors Random Error Size of error not constant & unpredictable . The reading is sometimes positive & sometimes negative from actual value. < Back Next > May arise from various causes. <ul><li>Parallax error – due to incorrect positioning of the eye when taking measurement </li></ul><ul><li>Changes in the surroundings; i.e. temperature, air circulation, lighting, magnetic field, etc. </li></ul>Can be reduced in several ways. <ul><li>Repeated measurements – taking mean value </li></ul><ul><li>Using mirror beneath pointer of instrument </li></ul>
13 Scientific Investigation The processes involved < Back Next > Making use of all human senses Initial explanation or conclusion Making smart guesses Testing in controlled situation Documentation of results in report Start End Observation Inference Hypothesis Experiment Conclusion
14 Scientific Experiment Steps involved in carrying out Experiment < Back Next > Aim Variables Apparatus Procedures Tabulation Analysis Suggest suitable questions Manipulated, responding, & fixed List apparatus/materials, arrangement Carry out experiment in proper order Documenting data obtained Analyze data through graphs, etc.
15 Summary < Back What you have learned: <ul><li>Understanding Physics </li></ul><ul><li>Physical Quantities </li></ul>Thank You 3. Measurements & Instruments 4. Scientific Investigations & Experiments
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