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GCSE Questions: Momentum

Q4. The diagram shows two ice hockey players moving towards each other. box They collide and then move off together.

 

(a) During the collision, the total momentum of the players is conserved.

What is meant by 'momentum is conserved'?

Momentum is conserved as the total momentum before the event equals the total momentum after the event.

[1 mark]

(b) Immediately after the collision the two players move together to the right.

Calculate the velocity of the two players immediately after the collision.

momentum of player A

pA= mAvA

pA= 78 x 7.5

pA= 585 kg m/s

momentum of player B

pB= mBvB

pB= 91 x (-5.5)

pB= – 500.5 kg m/s

 

Sum of momentum before the collision = – 500.5 + 585 = 84.5 kg m/s

Therefore after the collsion:

84.5 = (78 + 91) vA+B

vA+B = 84.5/169

vA+B = 0.5 (m/s)

[4 marks]

(c) The ice hockey players wear protective pads filled with foam.

Explain how the protective pads help to reduce injury when the players collide.

Ft = Δp

F = Δp/t

The force experienced is equal to the rate of change of momentum.

Protective pads increase the time taken to come to a stop during the collision, so the rate of change of momentum decreases reducing the force on the ice hockey player.

[3 marks]

[8 Marks TOTAL]