forces: momentum

Question 1

what is the momentum equation?

Answer 1

momentum( kgm/s) = mass(kg) X velocity (m/s)

Question 2

what does conservation of momentum mean in a collision?

Answer 2

in a closed system the total momentum before the collision is equal to the total momentum after the collision

Question 3

what equation links force and momentum?

Answer 3

force = change in momentum/time

mass x chnage in velcoity= change in moenmtum

OITHIS COULD ALSO BE FORCE= MASS X CHANGEIN VELOCITY / TIME

Question 4

when does a change in momentum occur?

Answer 4

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

Question 5

forces

Use the ideas of momentum to explain how the layer of foam reduces the risk of serious injury to a motorbike rider sliding at high speed into the support post. [ 3 marks]

this is an example but the mark scheme is that same for each question

Answer 5

the layer of foam increases the time taken to stop
this decreases rate of change in momentum
and so reduces the force (on the rider)

Question 6

why is braking hard dangerous?

Answer 6

When braking hard, there is a large deceleration
So a large force is felt on the passengers and the car
This can be dangerous, as the force felt can cause injury

Question 7

what is the saftey feature of a seat belt, crumple zone and airbags

Answer 7

**Seatbelts **
 Without these, when hard braking you will keep moving and not decelerate, causing to fly through the windshield
**Crumple zones **
 Without these, the car would be a solid metal block, which would immediately stop during a crash instead of “softening” the blow slightly
**Air Bags **
 Without these your head will whip forward during a crash, hitting the steering wheel or whipping back to hit the back of the head, which would cause serious neck energy