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Forces - Kinetic Energy of Objects
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

This GCSE Physics quiz on forces will challenge you on the kinetic energy of objects. All objects in motion have kinetic energy. The amount of kinetic energy depends on the speed they are moving and their mass and is measured in joules. When you compare two or more objects moving at the same speed, the heaviest will be the one that has the greater kinetic energy. Objects with more kinetic energy can do more work, which is why high speed collisions or collisions involving larger vehicles are more destructive.

When an object speeds up or slows down, its kinetic energy increases or decreases. When energy is transferred, it means that work has been done - the forces which cause a change in speed therefore do so by doing work. If friction and air resistance are ignored, the kinetic energy changes by an amount that is equal to the work done by the applied force.

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

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