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Fly down to question 10 to find out the speed of a bird of mass 3kg which has kinetic energy of 400J.

Forces - Kinetic Energy of Objects

Explore how moving objects store kinetic energy and how forces such as braking, friction and collisions change that energy in this exam-style GCSE Physics revision quiz.

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Fascinating Fact:

When brakes are applied to a vehicle, the braking force does work to remove kinetic energy and bring the vehicle to rest.

In GCSE Physics, you learn how forces transfer energy. Kinetic energy depends on an object's mass and speed, and braking systems use friction to remove this energy safely.

Key Terms

Kinetic energy: The energy a moving object has because of its mass and speed.
Work done: The energy transferred when a force moves an object through a distance.
Braking force: The force applied by brakes to slow down or stop a moving vehicle.

Frequently Asked Questions (Click to see answers)

What is the kinetic energy of an object?

The kinetic energy of an object is the energy it has because it is moving. In GCSE Physics it is calculated using the equation Ek = ½mv², in joules.

How does speed affect the kinetic energy of a vehicle?

Kinetic energy depends on the square of speed, so if the speed of a vehicle doubles, its kinetic energy becomes four times larger. This greatly increases stopping distances.

How do brakes reduce the kinetic energy of a car?

Brakes use friction between brake pads and wheels or discs. This braking force does work on the car, transferring kinetic energy into thermal energy in the brakes and tyres.

Try These Related Quizzes

1 .

What is the formula for kinetic energy?

K.E = m x v

K.E = ¹/₂ m x v²

K.E = m x v²

K.E = v x m²

Kinetic energy is determined by the speed and mass of an object

2 .

An athlete has a mass of 70 kg and is running at a speed of 10 m/s. What is their kinetic energy?

3500 J

7000 J

350 J

700 J

From the kinetic energy equation, it is half of 70 multiplied by 100

3 .

What is the mass of a ball which has 2.5 J of energy and is travelling at 5 m/s?

0.1 kg

0.2 kg

12.5 kg

62.5 kg

This needs you to rearrange the equation to isolate m. Once that is done, you can substitute in the figures from the question

4 .

Which formula correctly shows the relationship between speed and acceleration?

a = ^{(v - u)}/_t

a = ^{(u - v)}/_t

a = ^{(v - t)}/_u

a = v x u x t

Kinetic energy questions can sometimes seem a bit tricky as you often need to use more than one equation to arrive at the answer. The equation for acceleration is sometimes required, usually you will need to rearrange it to find the final velocity

5 .

What is the acceleration of a car as it increases in speed from 3 m/s to 10 m/s in a period of 5 seconds?

1.7 m/s²

1.4 m/s²

2 m/s²

0.6 m/s²

Straightforward substitution of the figures from the question, no need to rearrange the equation

6 .

What is the mass of a person who accelerates from 0 m/s to 10 m/s in 30 seconds? When travelling at 10 m/s, the person has a kinetic energy of 5000 J.

50 kg

68 kg

86 kg

100 kg

The first piece of information here is not actually needed to answer the question. Keep an eye out for this in your exams - cruel examiners sometimes try to catch you out!!! You can use the relationship between kinetic energy and speed to work out the mass

7 .

Which of the following can be converted into kinetic energy?

Gravitational potential energy

Elastic energy

Chemical energy

All of the above

You don't need to remember loads of examples of energy changes, you should be able to work them out from your knowledge and understanding of energy transfers

8 .

A ball is dropped from a height of 10 m and is pulled towards the Earth due to the gravitational field of the Earth. The strength of the Earth's gravitational field is 10 N/kg. What is the mass of the ball, if the ball has 100 J of GPE?

0.5 kg

1 kg

1.5 kg

1.8 kg

Even though the question is about a moving object, in this case, the equation for gravitational potential energy is sufficient to arrive at the answer

9 .

What is the weight of the ball in the question above?

1 N

9.81 N

10 N

15 N

Weight is calculated by multiplying the mass of an object by the strength of the gravitational field in which it lies. Although you know the more accurate figure for the acceleration due to gravity is 9.81 N/kg, the question refers to the previous one and so you must use the figure given in that

10 .

What is the speed of a bird of mass 3 kg which has kinetic energy of 400 J?

10 m/s

16 m/s

17 m/s

20 m/s

That's one quick bird!

You can find more about this topic by visiting BBC Bitesize - Kinetic and gravitational potential energy

Author: Martin Moore