Momentum (5.7) (M)

Question 1

What is momentum?

Answer 1

the product of mass and velocity

momentum = mass x velocity

Question 2

What is the conservation of momentum?

Answer 2

In a closed system, the total momentum before an event is equal to the total momentum after the event

may also need to refer to momentum being conserved in an exam q

Question 3

Why is it hard to prove momentum?

Answer 3

The conservation momentum law is only true if no other forces are acting

There is almost always other forces acting so this is hard to prove

Question 4

Give two examples of where momentum is conserved

Answer 4

collisions and explosions

Question 5

Explain using momentum why a gun recoils backwards when fired

Answer 5

When a cannon is fired, the cannon ball gains forward momentum and the cannon gains backward momentum.

Before the cannon is fired (the ‘event’), the total momentum is zero, because neither object is moving.

The total momentum of the cannon and the cannon ball after being fired is also zero (is conserved), with the cannon and cannon ball moving in opposite directions (state left or right in exam question)

Question 6

When does a change in momentum occur?

Answer 6

When a force acts on an object that is moving, or able to move

Question 7

Forward and backward momentum are (…)

Answer 7

equal

Question 8

How do protective pas reduce injury when ice hockey players collide?

Answer 8

they increase time taken to stop (during collision)

so rate of change of momentum decreases

reducing the (impact) force acting on the player

other safety features include crash mats, seat belts, air bags

Question 9

What assumption do you make when calculating the velocities of trollies after a collision?

Answer 9

that the conservation of momentum applies

no external forces apply or friction/air resistance is negligible