Unit 32 Newton's forces and the effects of forces

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  • + guest87b9b guest87b9b 9 months ago
    Thanks ^_^ Helped alot with my physics homework!
  • + mustamifaizah FAIZAH MUSTAMI 9 months ago
    This is an excellent presentation. Is it possible if you could email me this fantastic presentation. It’s sure will help my students to have a better understanding of Newton’s laws. Please send this ppt thro my email. I’ll be more than honored to mention you in my class.
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Unit 32 Newton's forces and the effects of forces - Presentation Transcript

  1. Science Interactive LTD Copyright 2005 Science Interactive LTD Science base multimedia CD-ROM for PC is a collection of 38 units or tools totalling over 1150 PowerPoint slides. Each unit covers a wide range of different delivery and learning styles, offering an exciting way to involve your pupils during lessons or revision sessions. All styles of teaching and learning are supported through use of high quality images, graphics, challenging exercises and questions. Units can be used in the classroom via an interactive whiteboard, data projector or used during individual study via a PC or school network. Science Interactive LTD. PO BOX 50764 LONDON NW6 9AT email: sales@science-interactive.co.uk web: www:science-interactive.co.uk Unit 1: The Digestive System Unit 20: Crude Oil and its Products Unit 2: The Circulatory System Unit 21: Rock Cycle Unit 3: Healthy Body and Immunity Unit 22: Elements, Molecules and Compounds Unit 4: The Respiratory System Unit 23: Ionic and Covalent Compounds Unit 5: Nervous System and the Senses Unit 24: The Halogens, their Uses and Compounds Unit 6: Human Homeostasis Unit 25: The Noble Gases, their Properties and Uses Unit 7: Hormones and the Endocrine System Unit 26: Rates of Reaction Unit 8: Drugs and Bad Body Maintenance Unit 27: Energy Unit 9: Photosynthesis in Green Plants Unit 28: Generating Electricity and its Domestic Use Unit 10: Water Transport in Plants Unit 29: Electricity Unit 11: Flow of Energy and Elements through the Environment Unit 30: Light and the Electromagnetic Spectrum Unit 12: Mitosis and Meiosis Unit 31: Radioactivity Unit 13: Inheritance and Selection Unit 32: Newton's Forces and the Effects of Forces Unit 14: Evolution and Human Impact Unit 33: Earth and Space Unit 15: Genetic Engineering Unit 34: The Earth and Plate Tectonics Unit 16: The Periodic Table and its Elements Unit 35: The Alkaline Earth Metals Unit 17: The Alkali Metals Unit 36: Sound and Hearing Unit 18: Metals and their Properties Unit 37: Natural Forces Unit 19: The Transitional Metals Unit 38: Cells, Tissue, Organs and Organs systems
  2. Science Interactive LTD Copyright 2005 Unit 32 Newton’s Forces and the Effects of Forces
  3. Unit 32: Newton’s Forces and the Effects of Forces Science Interactive LTD Copyright 2005 Understand: Keywords: That there are three types of natural forces, Forces, Newtons, Magnetism, Balanced, 1. magnetism, electrostatic and gravity. Unbalanced, Gravity, Electrostatic, Speed, That the size of a force is measured in Velocity, Terminal, Acceleration, 2. Newtons. Deceleration, Air resistance, Stopping, Some examples of balanced forces in action. Kinetic, Work done, Joules & Energy. 3. That a unbalanced force can make an object 4. accelerate, decelerate, change direction or change shape. How to calculate speed, velocity and 5. acceleration of a moving object. How to interpret distance, speed and velocity 6. time graphs. The stopping distance for cars at different 7. speeds and how factors like weather and road conditions affect overall stopping distances. What is air resistance and the factors that 8. determine its value. Newton’s first law of motion. 9. Newton’s second law of motion. 10. Newton’s third law of motion. 11. How to calculate the kinetic energy of a moving 12. object and work done by a force. Click mouse to begin Science Interactive LTD PO BOX 50764 LONDON NW6 9AT web: www.science-interactive.co.uk email: sales@science-interactive.co.uk
  4. Science Interactive LTD Copyright 2005 Natural forces There are three types of naturally occurring forces. These forces cannot be seen, but we can observe the effects of these forces, for example an a_______ falling towards Earth. In 1666, Newton was the first person to answer why objects fall to Earth. We can also see the effects of magnetic and electrostatic forces in action. Compared to g________, magnetic and electrostatic forces are relatively strong. Gravity is the smallest in magnitude of all the three forces. How could you design an experiment to show that magnetic and electrostatic forces are stronger than gravity ? Three types of forces: Word bank: apple gravity Gravity Magnetism Electrostatic Diagram Gravity is the force of attraction Magnetism is the attraction An electrostatic force is the Notes between objects with mass. between bar magnets or attraction or repulsion between Gravity is measured in Newtons. magnetic metals. There are only charged objects. Oppositely On Earth the gravitational force three metals which are charged objects attract one another is approximately 10 Newtons per magnetic: Iron nickel and whereas, objects with the same kilogram (10 Nkg-1) cobalt. charges repel one another.
  5. Science Interactive LTD Copyright 2005 Balanced forces one Although you cannot see forces, we can see the effects of forces and the resulting actions. If an unbalanced force acts on a object, it will either s_______ up, slow down, change direction or be squashed. When forces are balanced an object in motion will tend to stay in motion, and an object at rest will tend to stay at rest unless the object is acted upon by an outside force. When you are sitting on a chair, gravity exerts a f______ pulling your mass down, with the chair exerting an equal and opposite force on your body. Unless there is an external force acting on you, the chair and you will stay at rest. Give three other examples of objects that are at rest ? Balanced forces: Word bank: speed force Sitting down Lifting weights London bus 60,000 N 100 N Diagram 550 N Gravity Gravity Gravity Up thrust Up thrust Muscle 60,000 N 100 N 550 N Notes Gravity pulls downwards on Gravity pulls downward on the Gravity pulls downward on the the female with a force of 10 kg weight with a force of red bus with a force of 60,000 N. 550 N. The chair is pushing 100 N. The arm muscles are The ground is pushing upwards upwards with the same force pushing upwards on the weights with the same force of 60,000 N, of 550 N. with the same force of 100 N. preventing the bus from sinking.
  6. Science Interactive LTD Copyright 2005 Balanced forces two Understanding balanced forces is simple. We can use arrows to represent the size and direction of a force. The arrow shows the direction of the force with the size of the force being given in newtons (N) An object will stay at rest or not start to move, if the forces acting on it are balanced. What is more difficult to understand, is that an object will continue in m_______ at a s_______ speed when the forces are balanced. A cyclist will achieve a steady speed, where the force applied by the muscles through the gears and wheels is equal to the force of internal resistance and air resistance. Why is it easier to ride behind of a group of cyclists...Explain ? Balanced forces: Word bank: motion steady Harrier Jump Jet Boat sailing Building 3,000,000 N 60,000 N Diagram 30,000 N Gravity Gravity Gravity Up thrust Up thrust Up thrust 3,000,000 N 60,000 N 30,000 N Gravity pulls downward on Gravity pulls downward on the Gravity pulls downward on the Notes the jet with a force of boat with a force of 60,000 N. building with a force of 30,000 N. The thrust of the The up thrust from the water is 3,000,000 N. The ground or jet engines is pushing pushing upwards on the boat building foundations are pushing upwards on the jet with the with the same force of upwards with the same force of same force of 30,000 N. 60,000 N. 3,000,000 N.
  7. Science Interactive LTD Copyright 2005 Unbalanced forces one Although you cannot see forces, we can see the effects of forces and the resulting actions. If an unbalanced force acts on a object, it will either speed up, slow down, change direction or be squashed. On a roller coaster, g________ and the forces it exerts on your body will accelerate you from the start giving you the sensation of falling. Rapid a____________, twisting and turning gives you that sensation of a near vertical drop whilst still being safe. The force of gravity is far bigger than the force of friction between the moving parts. Why would a roller coaster on the moon’s surface be less scary ? Unbalanced forces: Word bank: gravity acceleration Roller Coaster Sprinters Free Falling Diagram 750 N 5,000 N Gravity Gravity 400 N 50 N Pull Push Air resistance Friction 250 N 750 N In this example, two forces In this example, two forces exists; In this example, two forces exists; Notes exists; Gravity and friction. The work done by the muscles and Gravity and air friction. The largest force is gravity pulling internal friction. The largest force largest force is gravity pulling the the mass of the roller coaster is produced by muscles propelling mass of the parachutist and people downwards at forward the sprinter along the downwards at an acceleration rate track at a speed of around 10 ms-1. 10 m/s2. (ignoring air resistance) of 10 m/s2 (ignoring air resistance)
  8. Science Interactive LTD Copyright 2005 Unbalanced forces two An unbalanced force provided by a car or lorry’s combustion engine can accelerate the moving vehicle in a forward direction. Engines provide the force to move vehicles like a car forward. This force is sufficient to overcome the internal r___________ of all the moving parts, the friction between the tyres and the road surface and air resistance as the car moves forward. Continue to put you foot on the accelerator pedal and the car reaches a maximum top speed. This is where the force of the e________ is equal to the drag created by the combined internal resistance and air resistance. Why are cars designed with a streamlined shape ? Unbalanced forces: Word bank: resistance engine Crashes Burn out Space shuttle launch Diagram 1,000,000 N Gravity Thrust Push Pull Push Wall strength 2,000,000 N 12,500 N 25,000 N 2,500 N 10,000 N In this example, two forces In this example two forces exist. In this example two forces exist. Notes exists. The forward push of the The forward push of the engine The upward thrust provided by the car and the wall’s strength. The and the friction between the tyres shuttle engines and the downward largest force is the forward push and tarmac. The largest force is pull of gravity on the shuttles of the car which is far higher the forward push of the engine mass. The largest force is the than the overall strength of the which drives the wheels during upward thrust of the shuttle wall. this burnout. engines.
  9. Science Interactive LTD Copyright 2005 Working with resultant forces Both the size and the direction of a force is important. A force is called a vector quantity. We can show the direction of the force by using an arrow drawn in a particular direction. The size of the force acting in any given d__________ can be indicated using a scale – for example, one centimetre for one Newton or by writing above the arrow, the size of the force in Newtons. Forces are always in pairs, so the resultant or overall force must be calculated. Work through these examples, giving your answers in Newtons ? Resultant forces: Word bank: direction Problem one Problem two Problem three 750 N 10 N 8000 N Gravity Gravity Gravity 20 N 2N Friction Forward 1kg Forward push Air resistance Air resistance 450 N 20000 N Up thrust Up thrust 200 N 10 N 8000 N A gravitational force of 750 N is There are four forces acting on a car: (i) There are four forces acting on the acting on the free falling man. Air Downward force of 8000 N, (ii) Upward one kilogram block: (i) Downward resistance acts in the opposite force of 8000 N, (iii) Forward engine force of 10 N, (ii) Upward force of direction with a value of 200 N. The force of 20,000 N (iv) Air resistance 10 N, (iii) Forward push of 20 N (iv) resultant force acting downwards force of 450 N. Work out the total Friction force of 2 N. Work out the and accelerating the parachutist is resultant force. Which way would the total resultant force. Which way 750 N -200 N = 550 N. car move ? would the block move ?
  10. Science Interactive LTD Copyright 2005 Forces and the effects of forces Forces cannot be directly observed, but the effects of a force can. A force measured in newtons exerted on an object can result in many different resultant actions. Forces affect the way objects move. You cannot see a force that changes an objects s________ or direction. A car accelerates forwards due the force exerted by the car’s engine on the front wheels. If you continue to accelerate, the car will achieve its maximum top speed, where the force of the e_________ is equal to the force of internal resistance and air resistance. If you apply a breaking force the car will slow to a stop Why do fast cars have the best brakes fitted ? Forces and the effects of forces: Word bank: speed engine Speed Velocity Acceleration Deceleration Diagram ms-1 ms-1 (0 to 3600) m/s2 -m/s2 Units Speed describes the distance Acceleration describes the change of Deceleration is the Notes travelled by an object and the time velocity and the time taken for that change in velocity taken. Velocity describes the change to occur. Constant acceleration when objects slow distance travelled and the time taken, gives a straight line, whereas changing down. It always but it also describes the direction of acceleration gives a curved line on a has a negative travel. velocity time graphs. value.
  11. Science Interactive LTD Copyright 2005 Speed one The speed of a moving object describes the distance travelled in metres over time in seconds. Knowing the speed of an object, allows you to calculate how long it will take the moving object to cover a certain d_________. Calculating the speed in metres per second (ms-1) of an object is simple using the following formula: Distance travelled (m) Units for speed = ms-1 Speed = Time taken (s) Calculating speed: Word bank: distance Lorry Sports car Cyclist Sprinter Diagram Distance (m) 2000 m 2000 m 2000 m 2000 m Time taken (s) 150 s 60 s 200 s 400 s Speed (ms-1) _____________ ? _____________ ? _____________ ? _____________ ? Notes Using the equation above, work out the speed of the lorry, sports car, cyclist and sprinter. Also calculate how long in time, it would take each object to cover 10 km (10,000 m)
  12. Science Interactive LTD Copyright 2005 Speed two Distance time graphs show distance travelled over time. The graph below shows a bus journey: The bus left the depot and took 200 seconds to travel 150 metres to a set of traffic lights. The bus waited here for 200 seconds while the lights changed to green. The bus then took a further 50 seconds to travel 100 metres. It then took 200 seconds to travel 50 metres and then a further 100 seconds to travel a further 100 metres. It then stopped back at the bus station. The total time for the journey was 750 seconds with the total distance covered being 400 metres. Distance time graphs: Displaying the bus journey using distance time graphs F Diagram 400 E Distance travelled (m) 350 D 300 250 C 200 B 150 A 100 50 0 0 100 200 300 400 500 600 700 800 Time taken (s) Table Distance travelled (m) 0 150 150 250 300 400 400 Time taken (s) 0 200 400 450 650 750 800 Calculate the following from the information given above: (a) Work out the average speed for the Notes entire bus journey. (b) At what point was the bus travelling the fastest speed (c) At what point was the bus travelling at its slowest speed. (d) For how many seconds in total was the bus at rest.
  13. Science Interactive LTD Copyright 2005 Speed three Using distance time graphs, you can see that the steeper the slope, the greater the object’s speed. We can use the gradient of the slope to calculate the speed of the moving object: Change in y (distance) Units for speed = ms-1 Speed = Gradient of distance time graph Gradient = Change in x (time) Using the graph, the speed at point C is worked out by dividing the distance travelled (250 m..change in y) by the time taken (250 s..change in x) This gives a speed or gradient of 1 ms-1. Speed and gradients: Distance time graph Distance time graphs A B D distance (m) distance (m) 400 Distance travelled (m) 350 C 300 250m 250 time (s) 200 B time (s) 150 C D A 250s 100 distance (m) distance (m) 50 0 0 100 200 300 400 500 600 700 800 Time taken (s) time (s) time (s) Calculate the following from the information given above: (a) Work out speed or gradient of the moving object at points A and B. (b) Work out the total distance travelled. (c) Work out the average speed of the moving object over the 700 seconds. (d) Which graphs (A, B, C or D) shows an object with (i) the lowest speed (ii) the highest speed (iii) zero speed.
  14. Science Interactive LTD Copyright 2005 Using distance time graphs Using distance time graphs is simple. The information provided by the graph tells us the speed or velocity of the moving object and the total d__________ travelled over time. You can see that the steeper the slope, the greater the object’s speed. We can use the g__________ of the slope to calculate the speed of the object. Also the total distance travelled by the moving object can be determined by using the graph. Using distance time graphs: Word bank: distance gradient Distance time graph Questions Question Answer B A 400 Which objects are not moving at all at the end ? 300 Which object is moving at the fastest Distance travelled (m) speed at the end ? C Which object took 800 seconds to travel 200 400 metres. Calculate its average speed. 100 Which object stops moving after 300 D seconds ? 0 Which object travels the least distance. 0 100 200 300 400 500 600 700 800 Calculate its average speed ? Time taken (s) Remember the following equation: Change in y (distance) Units for speed = ms-1 Speed = Gradient of distance time graph Gradient = Change in x (time)
  15. Science Interactive LTD Copyright 2005 Velocity The speed of an object tells us how fast its travelling (distance travelled over time taken), whereas using velocity tells us the speed of an object and the d___________ it is travelling. The direction of an object can be given quite simply as towards or away from us, or as a bearing having a value from 0 to 360 degrees. Distance travelled (m) Units for velocity = ms-1 (0 to 360o) + Direction (0 to 360o) Velocity = Time taken (s) Velocity: Word bank: direction Motorway traffic Coming towards you Going away from you Diagram Motorway traffic is a good Notes A sports car that is coming A sports car that is going away example of how velocity gives toward you at very high from you at very high velocity us more information than velocity may cause you to would cause you no anxiety at speed. In the fast lane, in both move out of its path. How all. How would you say away directions the speed is the same would you say towards you from you using degrees (0 to at 70 mph, but the direction is using degrees (0 to 3600) ? 3600) ? opposite being north or south.
  16. Science Interactive LTD Copyright 2005 Changing velocity one Moving objects change their velocity (accelerate or decelerate) when they move from rest to a steady velocity and then back to rest again. Using a v_________ time graph, we can show how the velocity of a moving object changes with time. Care must be taken, because velocity time graphs are much more complicated, when compared to distance time graphs. The velocity time graph below shows a car accelerating from 0 ms-1 to 35 ms-1 over 20 seconds to join the motorway and then maintaining a ‘steady speed’ of 35 ms-1 for a further 60 seconds. Changing velocity: Word bank: velocity velocity time graph...car Acceleration 0 to 60 mph in 3.5 secs 0 to 60 mph in 22 secs 40 Steady velocity 30 ing Velocity (ms-1) ra t 20 ele 0 to 20 mph in 2 secs 0 to 60 mph in 2.9 secs c part b part a Ac 10 0 0 10 20 30 40 50 60 70 80 Time taken (s) The graph can be separated into two parts: Part A The car is speeding up from rest (0 ms-1) to a final velocity of 35 ms-1 over a period of 20 seconds. It has a constant acceleration giving the graph a straight line appearance. The steeper the slope the greater the acceleration. Part B When the car has joined the fast lane, it travels at a constant speed of 35 ms-1 for a further 60 seconds. At a constant velocity, the graph is a horizontal straight line. From the graph, find the car’s velocity after 5 and 10 seconds.
  17. Science Interactive LTD Copyright 2005 Changing velocity two Just like a distance time graph, we can use a velocity time graph to find out how far in metres an object travels. Working out the a_______ under the graph will give us the total distance travelled. In the example below, it is easier to break the graph into two parts, a triangle and a rectangle. Work out the area of both and then add one to the other to find out the total d__________ travelled. Work out the total distance travelled using the following formulae: Area of rectangle = base x height Area of a triangle = ½ base x height Changing velocity: Word bank: area distance Distance time graph...car Working out total distance travelled 40 Steady velocity ½ x base x height 30 ing Velocity (ms-1) ra t 20 ele c part b part a Ac 10 base x height 0 0 10 20 30 40 50 60 70 80 Time taken (s) Working out the area of both parts gives us the total distance travelled by the car: Area of a triangle = ½ base x height ½ x 20 x 35 = 350 m 350 m Part A: Area of rectangle = base x height 60 x 35 = 2100 m 2100 m Part B: (Distance travelled) Total _______________ ?
  18. Science Interactive LTD Copyright 2005 Acceleration one Acceleration of a object is the change in velocity over a certain time period. Calculating acceleration requires the following information: Starting velocity (v), final velocity (u) and the t______ taken for that change to occur (t) Calculating the acceleration of an object is simple using the following formula: Final velocity (v) – Staring velocity (u) v –u Units for acceleration = m/s2 Acceleration = Time taken for change t Acceleration: Word bank: time Sports car Sprinters Free falling Cyclist Diagram 20 ms-1 0 ms-1 0 ms-1 5 ms-1 Starting velocity 60 ms-1 10 ms-1 40 ms-1 15 ms-1 Final velocity Time taken 2 seconds 0.5 seconds 4 seconds 2 seconds Acceleration 60-20/2 = 20 m/s2 _______________ ? _______________ ? _______________ ? Notes Work out the acceleration of each moving object by dividing the change in velocity by the time taken for that change to occur. Units for acceleration should be m/s2.
  19. Science Interactive LTD Copyright 2005 Acceleration two Velocity time graphs show the changes in velocity over time. The graph shows a cyclist’s journey: The cyclist left his house and took 10 seconds to change his velocity from 0 ms-1 to 7.5 ms-1. He then travelled at a c________ velocity of 7.5 ms-1 for a further 30 seconds. He then accelerated from 7.5 ms-1 to 15 ms-1 taking 5 seconds. He then travelled at a constant velocity of 15 ms-1 for 10 seconds. He then decelerated from 15 ms-1 to complete rest (0 ms-1) over 10 seconds. He then remained at rest for 10 seconds. He then accelerated from rest to 5 ms-1 taking just 5 seconds, where he continued at a constant speed of 5 ms-1 for 10 seconds. Changes in velocity and acceleration: Word bank: constant Velocity time graph....cyclist Velocity time graphs A B velocity (ms-1) velocity (ms-1) 20 D 15 C Velocity (ms-1) time (s) B 10 time (s) E C D H A velocity (ms-1) velocity (ms-1) 5 G F 0 0 10 20 30 40 50 60 70 80 Time taken (s) time (s) time (s) Calculate the following from the information given above: (a) Work out the total distance travelled by the moving cyclist (From working out the total area beneath the line graph you can work out the total distance travelled (b) Which graphs (A,B,C or D) shows an object with (i) the lowest constant acceleration (ii) the highest constant acceleration (iii) Constant velocity, zero acceleration (iv) Constant deceleration.
  20. Science Interactive LTD Copyright 2005 Acceleration three Using velocity time graphs, you can see that the steeper the slope, the greater the object’s acceleration or deceleration. We can use the gradient of the s_______ to calculate the object’s change in velocity: Change in y (velocities) Acceleration = Gradient of the velocity time graph Units for acceleration = m/s2 Gradient = Change in x (time) Using the graph, the acceleration of the object at point C is worked out by dividing the change in velocity (30 ms-1 – 20 ms-1= 10 ms-1...change in y) by the time taken for that change to occur (15 s...change in x) This gives a acceleration or gradient of 0.67 m/s2. Changes in velocity and gradients: Word bank: slope Velocity time graph...car Working out acceleration 0 ms-1 Starting velocity 150 ms-1 40 Final velocity D Time taken 60 s 30 C Velocity (ms -1) Acceleration ________ ? 10ms -1 20 B E 0 ms-1 Starting velocity 15s A 10 20 ms-1 Final velocity 5 F 0 Time taken 4s 0 10 20 30 40 50 60 70 80 Time taken (s) Acceleration ________ ? Calculate the following from the information given above: (a) Work out the total distance travelled by the moving car (from working out the total area beneath the line graph you can work out the total distance travelled (b) Work out the acceleration values for the plane and the ice skater using the formula...Change in velocity/time taken for that change to occur...units m/s2.
  21. Science Interactive LTD Copyright 2005 Using velocity time graphs Using velocity time graphs is simple. The information provided by the graphs tells us the acceleration or change of velocity of the m_________ object and the total distanced travelled over time. You can see that the s________ the slope, the greater the object’s change in velocity. We can use the gradient of the slope to calculate the acceleration of the moving object. Also, the total area under the graph tells us the total distance travelled over time. Using velocity time graphs: Word bank: moving steeper Velocity time graph Questions Question Answer B 40 Which objects has the highest E constant acceleration ? D A 30 Which object has zero acceleration and a constant velocity of 20 m-1 ? C Which 20 object has changing Velocity (ms-1) acceleration over 800 seconds. 10 Which object accelerates to 30 ms-1, decelerates and then is at rest ? 0 Which object travels the greatest 0 100 200 300 400 500 600 700 800 Time taken (s) distance ? Remember the following equations: Change in y (velocities) Acceleration = Gradient of the velocity time graph Units for acceleration = m/s2 Gradient = Change in x (time)
  22. Science Interactive LTD Copyright 2005 Acceleration and gravity one A free falling object not subject to air resistance will accelerate to Earth at 9.81 m/s2. You may have heard of Galileo’s experiment, where he dropped a heavy and light ball with the same shape from the leaning tower of Pisa at the same time. He observed them falling, accelerating at the same r______ and hitting the ground at exactly same time. This is because all objects regardless of their mass accelerate at the same rate (assuming no air resistance.) In a vacuum, which would land first a feather or a coin ? Galileo’s experiment and the leaning tower of Pisa: Word bank: rate Leaning tower of Pisa Notes Calculation Galileo’s experiment: The two balls Time (s) Velocity with very different masses are 1 10 ms-1 released at the same time. They also hit the ground at the same time, 2 proving that all objects accelerate at a constant speed due to gravity and 3 regardless of their mass. 4 Calculation: Calculating acceleration, we can use a value of 10 m/s2. Work 5 out the velocity of the accelerating object after 1,2,3,4,5 & 6 seconds 6 assuming there is no air resistance. 10 What is the object’s final velocity ?
  23. Science Interactive LTD Copyright 2005 Acceleration and gravity two If you take a ride on any rollercoaster, at any theme park, designers exploit gravity and other forces to give you the ‘ride of your life.’ Gravity and the forces it exerts on your body will a__________ you from the start, giving you a sensation of falling. Rapid acceleration, twisting and turning gives you that sensation of a near vertical drop whilst still being safe. The force of gravity on a vertical drop rollercoaster pulls the m______ of the car and you downwards, accelerating you at nearly 10 m/s2. Why would a rollercoaster on the surface of Jupiter be much more exciting. If the value of g on Jupiter is 26 N/kg, what would your acceleration rate be ? Gravity and the rollercoaster: Word bank: accelerate mass Roller coaster Questions A 1: At which point does the ball have maximum kinetic energy and minimum gravitational potential energy ? 2: At which point does the ball B have maximum gravitational potential energy and zero kinetic energy ? D 3: At which point does the ball E C have zero kinetic energy ? 4: At which point does the ball have decreasing kinetic energy and increasing gravitational energy ?
  24. Science Interactive LTD Copyright 2005 Acceleration and gravity three Gravity on Earth causes all objects with a mass to fall and accelerate towards Earth’s surface. In practise, Earth’s atmosphere subjects all moving objects to air r___________. This is the upward push of atmospheric air molecules exerted on a falling object. It requires a large amount of energy to push the air molecules out of the way during free fall. Because of this special type of friction, a f___________ object will reach a final or terminal velocity of about 50 ms-1. Terminal velocity is where the forces of gravity pulling you downwards is equal and opposite, to the upward force of air resistance. This velocity is sufficient to kill you, should you fall from a high building or your parachute fail to open. Terminal velocity: Word bank: resistance falling Free fall Re-entry Asteroids Diagram Gravity Gravity Gravity Air resistance Air resistance Air resistance Free falling, without a Spacecraft can travel an amazing Asteroids, large lumps of space Notes parachute, gravity accelerates 30,000 km per hour on re-entry debris can travel at over 100,000 km you to Earth’s surface reaching causing the tip of the craft to per hour, largely burning up because a terminal velocity of 50 ms-1. warm to 1600oC. Without heat of heat caused by air resistance. proofing the re-entry vessel Most asteroids and meteors never Nothing beats the sensation of would fail. reach the Earth’s surface. free falling !
  25. Science Interactive LTD Copyright 2005 Deceleration one Velocity time graphs show the changes in velocity (acceleration and deceleration) travelled over time. The graph below shows a cyclist’s journey: The cyclist left his house and changed his velocity from 0 ms-1 to 7.5 ms-1 over 10 seconds. He then travelled at a constant velocity of 7.5ms-1 for a further 10 seconds. He then decelerated from 7.5 ms-1 to 2.5 ms-1 taking 5 seconds. He then travelled at a constant velocity of 2.5 ms-1 for 10 seconds. He then accelerated from 2.5 ms-1 to 15 ms-1 taking 10 seconds. He then remained at a constant velocity of 15 ms-1 for 10 seconds. He then decelerated from 15 ms-1 to rest (0 ms-1) taking a further 25 seconds. Changes in velocity and acceleration: Velocity time graph....cyclist Velocity time graphs A B velocity (ms-1) velocity (ms-1) 20 F 15 Velocity (ms-1) E time (s) 10 time (s) B G C D C A velocity (ms-1) velocity (ms-1) 5 D 0 0 10 20 30 40 50 60 70 80 Time taken (s) time (s) time (s) Calculate the following from the information given above: (a) Work out the total distance travelled by the moving cyclist (From working out the total area beneath the line graph you can work out the total distance travelled (b) Which graphs (A,B,C or D) shows an object with (i) the lowest constant deceleration (ii) the highest constant deceleration (iii) Constant velocity, zero acceleration (iv) Constant acceleration.
  26. Science Interactive LTD Copyright 2005 Deceleration two Using velocity time graphs, you can see that the steeper the slope, the greater the object’s acceleration or deceleration. We can use the gradient of the slope to calculate the change in velocity of the object: Change in y (velocities) Deceleration = Gradient of the velocity time graph Gradient = Units for deceleration = -m/s2 Change in x (time) Using the graph, the deceleration of the object at point C is worked out by dividing the change in velocity (30 ms-1 – 15 ms-1= -15 ms-1...change in y) by the time taken for that change to occur (20 s...change in x) This gives a deceleration or gradient of -0.75 m/s2. Changes in velocity and gradients: Velocity time graph...car Working out deceleration 25 ms-1 Starting velocity 40 0 ms-1 Final velocity 20s B Time taken 0.1 s 30 Velocity (ms -1) C Deceleration ________ ? -15ms -1 20 A D 300 ms-1 Starting velocity E 10 0 ms-1 Final velocity 5 0 Time taken 25 s 0 10 20 30 40 50 60 70 80 Time taken (s) Deceleration ________ ? Calculate the following from the information given above: (a) Work out the total distance travelled by the moving car (from working out the total area beneath the line graph you can work out the total distance travelled (b) Work out the deceleration or gradient of the moving object at point E. (c) Work out the deceleration over time of the car hitting the lamp post and the plane landing.
  27. Science Interactive LTD Copyright 2005 Stopping distances one National speed limits apply to all roads in the United Kingdom. The speed limit is the absolute maximum and does not mean it is safe to d_____ at that speed irrespective of road and weather conditions. Driving at speeds too fast for the road and traffic conditions can be dangerous. The overall stopping distance is the sum of the distance travelled by your car, when you are reacting to an incident and the actual d_________ travelled whilst your brakes slow and eventually stop your car. At 70 mph, the overall stopping distance is a huge 96 metres, almost the length of a football pitch. What factors may lead to an increase in your thinking or stopping distance ? Stopping distances for cars in dry weather: Word bank: drive distance Total distance Speed Thinking distance and Stopping distance 20 mph 12 metres 6 metres 6 metres 30 mph 23 metres 14 metres 9 metres 40 mph 36 metres 24 metres 12 metres 50 mph 53 metres 38 metres 15 metres 60 mph 73 metres 55 metres 18 metres 70 mph 96 metres 75 metres 21 metres Notes Overall stopping distances are published for cars travelling at the above speeds. These stopping distance assume that there is good visibility, your brakes and tyres are in good working order and that the road conditions are dry.
  28. Science Interactive LTD Copyright 2005 Stopping distances two The speed limit is the absolute maximum and does not mean it is safe to drive at that speed irrespective of road and weather conditions. Your s__________ distance can be affected by road and traffic conditions, for example a wet road surface can almost double you stopping distance. You should always reduce your speed when the road layout or conditions presents hazards, such as sharing the road with pedestrians, cyclists, children, motorcyclists and other c______. Driving at night requires caution, as it is harder to see other road users. How might drinking alcohol affect your overall stopping distance and why is there no safe limit when you are driving a car ? Factors affecting stopping distances for cars: Word bank: stopping cars Weather conditions Alcohol Other road users Diagram The weather, the amount of alcohol you drink and other road users can all affect how quickly you Notes can bring you car to a halt. Alcohol affects your reaction or thinking time. This is why the government has set a legal limit of the amount of alcohol you can consume whilst driving. Normal road conditions 24 metres 12 metres Wet road conditions 38 metres 24 metres 12 metres When travelling on a wet road surface, your braking distance can almost double. During heavy rain, Notes speed limits on motorways are reduced for safer driving.
  29. Science Interactive LTD Copyright 2005 What is friction Ordinary friction between objects can be thought of as arising from surface roughness. Although two objects can appear to have relatively smooth surfaces, under the microscope, their surfaces can be extremely rough or pitted. This unevenness causes friction between moving objects, for example an engine piston moving inside a cylinder. Friction causes heat to build up as an object’s atoms or molecules gain kinetic energy. Try this: rub your hands together...do they become warm ? Useful and unwanted friction: Example one Example two Example three Example four Diagram Useful Useful Unwanted Unwanted Friction between the Friction between the Friction between the skier The friction between brake plate and the disc climbing axe and the ice and the ice slows down suitcase wheels and the slows the car down keeps the ice climber the downhill skier. How ground slows down converting the car’s pictured here from falling can you make the skies progress. How do wheel kinetic energy into heat. to the ground. faster ? bearings reduce friction ?
  30. Science Interactive LTD Copyright 2005 What is air resistance Ordinary air resistance is the force that acts against anything that moves through the atmosphere or air. Moving objects have to push past air molecules when they are moving forward. This force becomes larger in magnitude when an object increases its speed. It can be reduced by an object having a more aerodynamic shape, for example a sports car has a very low profile and a smooth pointed front. When the car travels at high speeds, air resistance is kept low. Streamlining also works when travelling through water. Explain why swimmers often shave their hair during competition ? Air resistance and car design: Beetle (Top speed 200 kmhr-1) Porsche (Top speed 240 kmhr-1) 4 x 4 (Top speed 170 kmhr-1) Diagram Notes Overcoming air resistance at high speeds requires an aerodynamic shape. Sports cars are designed so that their shape allows air to flow over and around their body therefore reducing air resistance. This and the fact that they have large powerful engines allows them to achieve very high top speeds. How can you say that the shape of the other two cars is related to their top speeds ?
  31. Science Interactive LTD Copyright 2005 Falling objects and air resistance As an object falls through air, it usually encounters some degree of air resistance. Air resistance is the result of collisions of the object's leading surface with air molecules. The actual amount of air resistance encountered by the object is dependent upon a variety of factors. To keep the topic simple, it can be said that the two most common factors which have a direct effect upon the amount of air resistance are the speed of the object and the cross sectional area of the object. Therefore both increased speed and cross sectional area of a moving object results in an increased amount of air resistance. Falling objects and air resistance: Start Middle End Using parachutes Diagram 750 N 750 N 750 N Gravity Gravity Gravity Air resistance Air resistance Air resistance 550 N 750 N 250 N At the start of the jump, the air resistance is low and the free faller accelerates Parachutes have a large downwards. As his speed increases, the air resistance increases, slowing his cross sectional profile acceleration. Eventually the air resistance force will be equal and opposite to which increases the air the downward force due to gravity. At this point the free faller’s speed remains resistance. This lowers constant. your descent speed.
  32. Science Interactive LTD Copyright 2005 Understanding terminal velocity Why does an object which is falling and encountering air resistance eventually reach terminal velocity ? As an object falls, it picks up speed. The increase in speed leads to an increase in the amount of air resistance. Eventually, the force of air resistance becomes large enough to balance the force of gravity. At this instant in time, the net force on the falling object is 0 Newtons, therefore the object stops accelerating and the objects velocity remains constant. The velocity at which this happens is called the ‘terminal velocity.’ Which object would have a lower terminal velocity when falling through air, a 10 g feather or a 10 g coin ? Terminal velocity: Terminal velocity Falling with parachute Falling without parachute Diagram C A Gravity 60 60 45 45 30 30 Velocity (ms-1) Velocity (ms-1) Air resistance B 15 15 0 0 0 Time (s) Time (s) 50 100 0 50 100 Notes Free falling, without a Falling with parachute: Speed Falling without parachute: Speed parachute, gravity accelerates increases reaching terminal increases reaching terminal you to Earth’s surface reaching velocity at A, where parachute velocity at C, where the force of a terminal velocity of about deployment reduces speed air resistance becomes large 50 ms-1. Nothing beats the reaching a lower terminal velocity enough to balance the force of at B. gravity. sensation of free falling !
  33. Science Interactive LTD Copyright 2005 Newton and forces Newton was born December 25th 1642. He was admitted in June 1661 to Trinity College, Cambridge. Between 1664 and 1666, Newton lay the groundwork of his theory of calculus, laws of m______, theory of colour, and theory of universal gravitation. It is during these few years that nearly all of Newton's lifetime scientific achievements took shape. Shortly thereafter, he designed and constructed the first reflecting telescope. Newton's key insight of 1666, namely that gravity, the force felt here on Earth is the same force that held the planets in their orbits around the Sun. Newton developed in detail these ideas, providing a theoretical framework for the Laws of planetary motion. Newton made numerous discoveries in the field of optics, especially with respect to light and colours. He was knighted in 1705 and died on 20th March 1727. Sir Isaac Netwon and Newton’s laws: Word bank: motion Newton Newton’s Laws of Motion Newton’s first Law: Diagram Newton’s first law states: ‘An object in motion tends to stay in motion, and an object at rest tends to stay at rest, unless the object is acted upon by an outside force.’ Newton’s second Law: Newton’s second law states that ‘Acceleration = force/mass.’ This law relates the force exerted on an object, its mass and resulting acceleration. Newton's ideas were written Notes between 1684 and 1686 and Newton’s third Law: published by Edmond Halley, Newton’s third law states that: ‘Every action has an equal of cometary fame. His thesis and opposite action.’ This law relates how if you’re falling to was titled: Philosophiae Earth, the Earth is also falling toward you ! Naturalis Principia Mathematica
  34. Science Interactive LTD Copyright 2005 Newton’s first law Newton’s first law states “An object in motion tends to stay in motion, and an object at rest tends to stay at rest, unless the object is acted upon by an outside force.” For example, an object at r_______ will stay at rest unless a force is applied to it. If it is moving, it will keep on moving at a constant speed and in a straight line. Name two types of forces acting on a stationary car: Draw a diagram of these forces...are they equal in size ? Newton’s first law: Word bank: rest Example one Example two Example three Diagram Astronaut at rest: At rest: Constant speed: Notes In this example, the astronaut The archer exerts a force by As the space probe gains speed, due will remain motionless unless using his skeletal muscle on the to the pull of gravity, friction due to an outside force acts upon him bow and arrow which is equal in air resistance increases, so that the during his space walk. How size but opposite to the elastic two forces are equal, but opposite. would the astronaut make pull of the bow. What will The probe stops accelerating and himself go forwards ? happen when he lets go ? travels at a constant speed.
  35. Science Interactive LTD Copyright 2005 Newton’s second law one Newton’s second law states that Acceleration = Force/Mass or F =ma Acceleration = Force (N)/ Mass (kg) Units for acceleration = m/s2 When the forces acting on an object is unbalanced, the resultant force causes the object to change its speed or velocity. It accelerates or decelerates. How fast it accelerates or decelerates depends on: Mass (the more mass an object has for the same force, the less it accelerates) Resultant Force (the greater the force acting on an object with the same mass, the faster it will accelerate) Newton’s second law: Example one Example two Example three Diagram 1N 1 kg a = 1 m/s2 Having the biggest engine and The standard definition of a Buses are slow, although they Notes the lightest car gives formula Newton: One Newton is have a very powerful engine one drivers and their teams defined as the force which will delivering a lot of force, their like Ferrari an advantage over give an object with the mass of mass is huge when compared to 1 kg, an acceleration of 1 m/s2. the other competitors. that of a car.
  36. Science Interactive LTD Copyright 2005 Newton’s second law two Working out the acceleration of a moving object with a known fixed mass and a known force acting upon it is easy. Newton’s second law tell us that the acceleration of an object is equal to force divided by its mass. Work out the acceleration of the different moving vehicles which all have different masses and resultant forces acting upon them...explain why a lorry is slow to accelerate when compared to a bullet or even a cyclist ? Acceleration = Force (N)/ Mass (kg) Units for acceleration = m/s2 Working out acceleration: Lorry Bullet Motorbike Cyclist Diagram Force 90,000 N 20 N 12000 N 600 N Mass 30,000 kg 0.1 kg 800 kg 80 kg Acceleration = force/mass Acceleration = force/mass Acceleration = force/mass Acceleration = force/mass (m/s2) _______________________ ? _______________________ ? a= 90,000N/30,000 kg _______________________ ? ___________m/s2 ___________m/s2 = 3 m/s2 ___________m/s2
  37. Science Interactive LTD Copyright 2005 Newton’s third law Newton’s third law states “Every action has an equal and opposite re - action” Think about this. If you are falling towards Earth, then Newton’s third law states that there must be an e_______ and opposite reaction. Does the Earth move upwards towards you falling downwards ? Well yes it does, but its mass is huge, so the effect cannot be measured or seen. Another example, when you shoot a gun, the f____ that propels the bullet forwards also pushes you backwards a little. Again there is a great difference between the mass of a bullet and the person, but the effect can be seen. Why in movies do we know that they exaggerate this effect ? Newton’s third law: Word bank: equal force Example one Example two Example three Diagram Gun shot: Free falling: Rocket: Notes The force pushes you As you free fall, the Earth The thrust of the rocket’s engines backwards, as the bullet moves experiences an equal and opposite pushes against the Earth. As the forwards from the gun barrel. reaction, although because of rocket moves out to space, Earth Movies exaggerate this a great Earth’s huge mass it can’t be undergoes an equal and opposite deal for effect ! observed reaction.
  38. Science Interactive LTD Copyright 2005 Kinetic energy one Kinetic energy requires us to relate the velocity and mass of a moving object. Understanding the kinetic e________ of a car at different speeds, helps us understand why we have speed limits on the streets of our towns and villages. If a child is hit at 30 mph (approx 15 ms-1) the child has a 80% chance of surviving. If the same car hits the same child at 40 mph, the child has only a 20% chance of surviving. This is because we square the speed to work out the energy of the car moving at a certain speed. A car travelling at 40 mph imparts 10squared or 100 times the energy into a child’s body compared to a car travelling at 30 mph. Work out the kinetic energy of the car at different velocities...explain why around schools the speed limit is 20 mph ? Kinetic energy: Word bank: energy Car at 10 ms-1 Car at 15 ms-1 Car at 20 ms-1 Car at 30 ms-1 Diagram 30mph 60mph 40mph 20mph 10 ms-1 (approx 20 mph) 15 ms-1 (approx 30 mph) 20 ms-1 (approx 40 mph) 30 ms-1 (approx 60 mph) Speed Mass 800 kg 800 kg 800 kg 800 kg ½ x mass x (velocity)2 ½ x mass x (velocity)2 ½ x mass x (velocity)2 ½ x mass x (velocity)2 Kinetic energy (J) _______________________ ? _______________________ ? ½ x 800 kg x (10 ms-1)2 _______________________ ? ___________J ___________J = 40,000 J ___________J ? ? ?
  39. Science Interactive LTD Copyright 2005 Kinetic energy two All moving objects have kinetic energy. Kinetic energy requires us to relate the velocity and mass of a moving object. Therefore kinetic energy of a moving objects depends on its mass and velocity. If an object like a p_______ with a large mass travels at low speeds, it has a large kinetic energy. Also, if an object like a bullet with a low mass travels at very high speeds, it too will have a high kinetic energy. Work out the kinetic energy of the following moving vehicles which all have the same velocity...explain why being hit by a lorry at 20 ms-1 is much more likely to kill you than when you are hit by a cyclist at 20 ms-1 ? Kinetic energy: Word bank: plane Lorry Cyclist Car Plane Diagram 20 ms-1 20 ms-1 20 ms-1 20 ms-1 Speed Mass 30,000 kg 80 kg 800 kg 350,000 kg ½ x mass x (velocity)2 ½ x mass x (velocity)2 ½ x mass x (velocity)2 ½ x mass x (velocity)2 Kinetic energy (J) _______________________ ? _______________________ ? ½ x 30,000 kg x (20 ms-1)2 _______________________ ? ___________J ___________J = 6,000,000 J ___________J ? ? ?
  40. Science Interactive LTD Copyright 2005 Kinetic energy three All moving objects have kinetic energy. Kinetic energy requires us to relate the velocity and mass of a moving object. Therefore kinetic energy of a moving objects depends on its mass and velocity. Bullets kill you, not because of their m____, but because of their very high velocities. A tanker can crush you to death even if it moves at 0.1 ms-1 because it has a huge mass. A asteroid impacting with Earth, may cause climate change and mass extinction, because it has a high mass and velocity. Work out the kinetic energy of the different moving objects which have different velocities and masses...explain why a bullet can kill you, despite its low mass ? Kinetic energy: Word bank: mass Bullet at 500 ms-1 Tanker at 0.1 ms-1 Car at 30 ms-1 Meteor at 3000 ms-1 Diagram 60mph 500 ms-1 0.1 ms-1 30 ms-1 3000 ms-1 Speed Mass 0.1 kg 5,000,000 kg 800 kg 100,000 kg ½ x mass x (velocity)2 ½ x mass x (velocity)2 ½ x mass x (velocity)2 ½ x mass x (velocity)2 Kinetic energy (J) _______________________ ? _______________________ ? ½ x 0.1 kg x (500 ms-1)2 _______________________ ? ___________J ___________J = 25,000 J ___________J ? ? ?
  41. Science Interactive LTD Copyright 2005 Kinetic energy four An unbalanced force provided by a combustion engine found in cars, trains or lorries can accelerate a moving vehicle forwards increasing its kinetic energy. During a car journey, c_________ energy in the fuel is transformed to kinetic energy. The greater the speed of the car, the more fuel the engine uses. Some of the chemical energy is wasted overcoming internal f_______ and air resistance. When a car slows, the kinetic energy is converted into heat energy by the brakes. The force of friction causes this energy transfer. Why do lorries and buses consume more fuel than cars and motorbikes ? Work done: Word bank: chemical friction Converting chemical energy into kinetic energy Notes When we combust fuels like octane with oxygen, energy in the form of heat and kinetic energy is released. New substances are also produced including carbon dioxide 2C8H18 + 25O2 CO2 + 18H2O and water. Octane Oxygen Carbon dioxide Water A car over a journey of 80 minutes 4000,000 80,000 will have different kinetic energies. Chemical energy (J) Since its mass doesn’t change this Kinetic energy (J) 60,000 3000,000 B is linked to its velocity. As the 40,000 2000,000 C A journey proceeds, chemical energy F gradually reduces as petrol is 20,000 1000,000 E combusted in the engine to provide D 0 0 forward motion and overcome 0 10 20 30 40 50 60 70 80 internal friction and air resistance. Time taken (minutes)
  42. Science Interactive LTD Copyright 2005 Work done one Energy or a force is required to do work like lifting, pulling, pushing and stretching. In science, work is done if a force pushes, pulls, stretches or lifts an object with a mass. The amount of work done is always measured in joules. The result of doing work, means that an objects gains the following types of energy: Kinetic energy Gravitation potential energy Heat energy Units for work done = Joules Look at these examples and determine what kind of energy has been given to the object as a result of doing work ? Work done: Pushing Pulling Lifting Stretching Pushing: When you push a car or an object, the car starts to move. Energy has been transferred to the car as kinetic energy. Pulling: When you pull the rope, the rope will start to move. Energy has been transferred as kinetic energy. Lifting: When a object is lifted above ground level by using a force, the gravitational potential energy of the object starts to increase. Stretching: If you stretch something it gains elastic potential energy. Repeated stretching, because of friction between the molecules transfers energy into heat energy.
  43. Science Interactive LTD Copyright 2005 Work done two The amount of work done is equal to the amount of energy transferred and is always measured in joules. A large force t_________ more energy and the further the distance it moves, the more energy is transferred. Therefore the amount of work done is the force multiplied by the distance moved. Work done = force (N) x distance moved in the direction of the force (m) Units for work done = Joules Look at these examples and determine what kind of energy has been given to the object as a result of doing work ? Work done: Word bank: transfers Example one Example two Example three Example four Lifting Example five Example six Example seven Example eight
  44. Science Interactive LTD Copyright 2005 Work done three The amount of work done is worked out using the following equation: Work done = force (N) x distance moved in the direction of the force (m) Units for work done = Joules When we are calculating, the amount of w_____ done a body does to lift a mass vertically upwards against gravity, this work done is transferred into gravitational potential energy. When we move sides ways, no work is done because our bodies are not getting any higher. Look at these examples and determine the amount of work done. Remember vertical distance only ! Work done: Word bank: work Example one Calculation Example two Calculation A pulley is a device A man weighing which can lift heavy 600 N walks up four loads. The pulley in flights of stairs. the diagram, lifts a These stairs climb a Vertical distance 20 m Vertical distance 10 m 100 N weight through total vertical distance a vertical distance of of 20 metres. Work 10 metres. Work out out the work done the work done using using the above the above formula ? formula ? Remember the formula: Remember the formula: Work done = force x Work done = force x 100 N distance moved distance moved 600 N
  45. Science Interactive LTD Copyright 2005 Work done four Look at these examples and determine the amount of work done. Use the equation below and give your answers in joules or kilojoules ? Work done = force (N) x distance moved in the direction of the force (m) Units for work done = Joules Work done: Problem one Problem two Problem three Problem four Diagram Car (8000 N) climbing A lift carrying 4 people A man (600 N) climbing A plane weighing an alpine pass that is over 50 m with a total the stairs ascending a 3,500,000 N climbing to 2000 m high. weight of 15,000 N. vertical height of 25 m. 10 km above sea level. Weight (N) 8,000 N 15,000 N 600 N 3,500,000 N Vertical 2000 m 50 m 25 m 10,000 m height (m) Calculation 8000 N x 2000 m Answer (J) 16,000,000 Joules ______________ ? ________________ ? _________________?
  46. Science Interactive LTD Copyright 2005 Extension questions and homework 1: Define the following terms: Force, Newton, Speed, Velocity, Acceleration & Deceleration. 2: Look at the velocity time graph. Complete the table. Question Answer B At which point is the cycle travelling at constant velocity ? 20 At which points is the cyclist accelerating ? 15 At which point is the cycle not moving ? V e lo c ity ( m s -1 ) A C 10 At which point is the cycle decelerating ? F What is the cycle’s highest velocity ? 5 E At A what is the average acceleration of the cyclist over 10 seconds. D 0 At B between 10 and 30 seconds what distance does the cycle travel ? 0 10 20 30 40 50 60 70 80 Time taken (s) How long in seconds is the cycle stationary for ? 3: Answer and explain the following: a) A machine gun recoils when it is fired. b) During a spacewalk, an astronaut begins to drift away from the space shuttle. How can he return using an aerosol spray c) When you walk forwards, you can move the planet Earth backwards. d) Give three examples of unbalanced and balanced forces in action. Draw one of each. e) Speedboats have sharper front ends than a ferry or a barge. f) Sliding down a rope can burn the skin on your hand.
  47. Science Interactive LTD Copyright 2005 4: Answer the following questions (Take g = 10 m/s2 = 10 N/kg where necessary.) (a) A car travels 200 m in 5 seconds: What is its average speed. (b) A car accelerates from 5 ms-1 to 25 ms-1 in 10 seconds. What is its acceleration. (c) Sketch a velocity-time graph of you walking to a bus stop for 2 minutes at a speed of 5 km/hr, catching the bus which then travels at 50 km/hr for 10 minutes, getting off and then running to school at 9 km/hr for 3 minutes. 5: The table gives some data for a grand prix motor-bike race at the start. Speed (ms-1) 0 10 20 28 36 49 64 65 65 65 Time (s) 0 1 2 3 4 5 6 7 8 9 (a) Plot a velocity-time graph. (b) What was the average acceleration between (i) 2-3 s (ii) 4-5s (iii) 8-9s 6: Answer the following questions. (a) The canary wharf tower is 400 metres high. Some jumps off. How long to they have to live. (b) Explain why parachutists and snowflakes do not fall with a constantly accelerating motion. (c) A car accelerates from rest (0 ms-1) to a final velocity of 10 ms-1 for 12 seconds. Calculate the final velocity. 7: A car is approaching a set of traffic lights. Three forces are acting upon it: (i) The forward force of the engine. 400 N (ii) The backward force of the brakes; 1200 N. (iii) Air resistance 200 N (a) Draw a diagram to show the forces acting on the car. (b) What is the unbalanced force acting on the car. (c) If the car’s mass is 650 kg work out its deceleration. Show your working out. (d) What is the car’s kinetic energy converted into as it slows down.
  48. Science Interactive LTD Copyright 2005 8: Answer the following questions: (a) Find out the thinking and stopping distance of a car travelling at 60mph. (b) What conditions may affect the braking distance. (c) Why is there a legal maximum on the amount of alcohol you can drink, before driving a car. 9: Answer the following questions: (a) A large bus carrying many passengers and a small car with just the driver are travelling at the same velocity along a main road. The traffic lights ahead turn red. Explain why the bus needs better brakes and a better braking force than the small car. (b) At the traffic lights, a lorry, bus, cyclist and motorbike accelerate when the lights turn back to green. Work out the acceleration of all from the following information. Which is the fastest...explain this. Diagram Force 90,000 N 70,000 N 12000 N 600 N Mass 30,000 kg 20,000 kg 800 kg 80 kg 10: Look at these graphs. They represent the way different quantities might differ when a coin is dropped to the ground. Graph yA yC yD yB time (s) time (s) time (s) time (s) Which graph represents: (a) The weight of the coin as it falls. (b) The resultant force acting on the coin. (c) The velocity of the coin as it falls. (d) The force of air resistance on the coin as it falls. Go to google.co.uk and find out about Newton’s life and his three laws of motion.

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