 # Momentum

In this worksheet, students explore momentum, and how it is used. Key stage:  KS 4

Curriculum topic:  Physics: Forces and Motion

Curriculum subtopic:  Speed

Difficulty level:   ### QUESTION 1 of 10

Moving objects have momentum. The more momentum an object has, the harder it is to change its direction. To calculate momentum you need to use the following formula:

momentum (kg m/s) = mass (kg) × velocity (m/s)

Total momentum stays the same in explosions and collisions, as long as no external forces act on the objects involved. When a car travels, everything in it has momentum; during a crash, forces act on passengers in the car and this can cause injury. If the time taken to change the momentum is increased, the forces on the bodies of passengers reduce. This is the role of seat belts, crumble zones and air bags.

To calculate the force involved in changing momentum, you can use the following equation: What do all moving objects have? Consider the introduction and write the word in the answer box below.

Is the following statement true or false?

The more momentum an object has, the harder it is to change its direction.

true

false

What happens to the total momentum in explosions and collisions, as long as no external forces act on the objects involved?

It decreases.

It increases.

It stays the same.

Calculate the momentum of an object if it has a mass of 80kg and moves with a velocity of 60m/s. Type just the number in the answer box below, but make sure you know the unit.

Calculate the momentum of an object if it has a mass of 100kg and moves with a velocity of 3m/s.

300 kg m/s

3000 kg m/s

30 kg m/s

How can the forces acting on passengers in a car be reduced to avoid injury in the case of an accident? Tick two boxes.

Increase the time taken to change the momentum.

Reduce the time taken to change momentum.

Wear a seat belt.

Move your seat forward.

Tick two features of car safety.

crumble zones

windscreen

steering wheel

air bags

What do you need to divide the change in momentum by to get the force needed to change it?

by the change in the forces acting on the system

by the time taken for change

by the momentum of all subjects and objects involved

A bullet with a mass of 0.05 kg leaves a gun at 2000m/s. If the gun’s mass is 2kg, what is the velocity of the recoil on the gun?

150 m/s

200 m/s

50 m/s

A 15 kg bicycle is travelling at 10m/s. What force is needed to bring it to a halt in 3s?

50 N

100 N

150 N

• Question 1

What do all moving objects have? Consider the introduction and write the word in the answer box below.

momentum
EDDIE SAYS
All moving objects have momentum.
• Question 2

Is the following statement true or false?

The more momentum an object has, the harder it is to change its direction.

true
EDDIE SAYS
The statement is true: the more momentum an object has, the harder it is to change its direction.
• Question 3

What happens to the total momentum in explosions and collisions, as long as no external forces act on the objects involved?

It stays the same.
EDDIE SAYS
The total momentum in explosions and collisions stays the same, as long as no external forces act on the objects involved.
• Question 4

Calculate the momentum of an object if it has a mass of 80kg and moves with a velocity of 60m/s. Type just the number in the answer box below, but make sure you know the unit.

4800
EDDIE SAYS
momentum = mass × velocity = 80 x 60 = 4800 kg m/s
• Question 5

Calculate the momentum of an object if it has a mass of 100kg and moves with a velocity of 3m/s.

300 kg m/s
EDDIE SAYS
momentum = mass × velocity = 100 x 3 = 300 kg m/s
• Question 6

How can the forces acting on passengers in a car be reduced to avoid injury in the case of an accident? Tick two boxes.

Increase the time taken to change the momentum.
Wear a seat belt.
EDDIE SAYS
The forces acting on passengers in a car can be reduced to avoid injury in the case of an accident by increasing the time taken to change the momentum, which is achieved by wearing a seat belt.
• Question 7

Tick two features of car safety.

crumble zones
air bags
EDDIE SAYS
Two features of car safety are crumble zones and air bags.
• Question 8

What do you need to divide the change in momentum by to get the force needed to change it?

by the time taken for change
EDDIE SAYS
You need to divide the change in momentum by the time taken for change to get the force needed to change it.
• Question 9

A bullet with a mass of 0.05 kg leaves a gun at 2000m/s. If the gun’s mass is 2kg, what is the velocity of the recoil on the gun?

50 m/s
EDDIE SAYS • Question 10

A 15 kg bicycle is travelling at 10m/s. What force is needed to bring it to a halt in 3s?

50 N
EDDIE SAYS
Momentum at start = 15 × 10 = 150 kg m/s
Momentum at end = 15 x 0 = 0 kg m/s
Change in momentum = 150 - 0 = 150 kg m/s ---- OR ----

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