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P2a Speaking & Listening Test
1. What effect can a single force have on an object?
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Change the speed
Change the direction of movement
Change the shape.
2. What does Newton’s first Law state?
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If there is no resultant force acting on an object, its motion will not change; it will remain stationary, or if
moving keep at constant speed in a straight line.
3. What is a vector quantity? How is it different to a scalar quantity?
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A vector quantity has size and direction.
A scalar has size only. For example, velocity is vector, speed is a scalar.
4. What causes drag, or air resistance?
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When an object moves through the air, it has to push the air particles out of the way.
The air particles put an opposing force on the object, causing drag.
When moving faster, more particles have to be moved each second, so the drag force increases with speed.
5. Explain why a moving car has top speed, or terminal velocity.
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The wheels make the car accelerate by transferring the thrust from the engine to the road.
As the car accelerates, the speed increases, so drag builds up.
The drag cancels out some of the driving force, so making the resultant force less, and the acceleration
reduces.
Eventually when fast enough, the drag force is equal and opposite to the driving force, and so there is no
resultant force.
There will be no acceleration as the resultant force is zero, and so the car will not speed up, or slow down, it
has reached its terminal speed.
A higher top speed can be obtained by streamlining the car.
This reduces the drag at a given speed. The speed at which drag equals the driving force will now be higher.
6. What is meant by the thinking distance?
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This is the distance travelled by a car whilst the driver is reacting to the stimulus telling him to apply the
brakes.
During this distance the car will travel at constant speed.
It is independent of the road conditions, tyre and brake condition and weather.
It is only altered by the speed, and by the driver.
7.
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What is meant by braking distance?
The distance travelled by the car from when the brakes are applied to when it stops.
The braking distance is altered by the condition of the brakes, the tyres, the road surface and the speed.
The thinking and braking distances combine to give the overall stopping distance.
8. When a car is stopped by its brakes, what are the energy changes?
 The kinetic energy of the car is removed by the brakes.
 Friction between the brakes and the wheel does work, and transfers the kinetic energy into heat energy in
the brakes and wheel.
9. How is distance travelled calculated from a velocity- time graph?
 By working out the area beneath the line.
10. What does the gradient of a velocity-time graph represent?
 The acceleration.
11. What does the gradient of a distance-time graph represent?
 The speed.
12. Which equation is used to calculate the force acting on a mass?
 F= m x a
13. What can you say about the forces acting on an object travelling at constant speed?
 Driving force is equal & opposite to the resistive force [s]
14.
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What is the weight of an object?
Weight is a force, it is the force of gravity acting on an object.
Weight= mass x gravitational field strength; W = m x g
On Earth, g = 10N/kg on the moon, g= 1.6 N/kg
15. When a material is stretched or compressed, what energy is stored in it?
 Elastic potential energy.
16. What does Hooke’s law say?
 The extension of an elastic material caused by a load is directly proportional to the force causing it, providing
that the limit of proportionality is not exceeded.
17. How much work is done by a force?
 work done = force x distance moved
18. What is the equation for kinetic energy?
 KE = 1/2mv2
19. What is the equation for gravitational potential energy
 PE = m x g x h
20. What is he rule about momentum in collisions?
 Momentum is conserved.
 This means that the momentum before the collision is the same as the momentum after the collision.
21. How does the crumple zone of a car reduce passenger injury?
 Force = the rate of change of momentum [F =change in momentum/time]
 In a collision, the crumple zone extends the time it takes to stop as it crumples. As the time is longer, the
braking force acting on the passengers is reduced.