5.7 Forces (Momentum)

Question 1

State the equation used to calculate an object’s momentum

Answer 1

Momentum = mass x velocity

Question 2

What is the unit used for momentum?

Answer 2

kg m/s (kilogram metres per second)

Question 3

In a closed system, what can be said about the momentum before and after a collision?

Answer 3

The total momentum before is equal to the total momentum afterwards

Question 4

State an equation linking change in momentum, force and time

Answer 4

Force x Time = Change in momentum

Question 5

What quantity is equal to the force experienced in a collision?

Answer 5

The rate of change of momentum

Question 6

If an object’s change of momentum is fixed, what is the only way to reduce the force that the object experiences?

Answer 6

Increase the length of time over which the change of momentum occurs

Question 7

Explain how a seatbelt improves a passenger’s safety during a collision?

Answer 7

• Passenger must decelerate from the vehicles velocity at impact to zero, meaning they undergo a fixed change of momentum
• the force they experience is equal to the rate of change of momentum
• seatbelts increase the time over which the force is applied, reducing the rate of change of momentum and therefore reducing the force experienced