Refer to Conceptual Example 3 as an aid in understanding this problem. A hockey

Question

Refer to Conceptual Example 3 as an aid in understanding this problem. A hockey goalie is standing on ice. Another player fires a puck (m = 0.18 kg) at the goalie with a velocity of+64 m/s

Refer to Conceptual Example 3 as an aid in understanding this problem. A hockey goalie is standing on ice. Another player fires a puck (m = 0.18 kg) at the goalie with a velocity of+64 m/s If the goalie catches the puck with his glove in a time of 8.0 times 10-3 s, what is the average force (magnitude and direction) exerted on the goalie by the puck? Instead of catching the puck, the goalie slaps it with his stick and returns the puck straight back to the player with a velocity of ?64 m/s. The puck and stick are in contact for a time of 8.0 times 10-3 s. Now what is the average force exerted on the goalie by the puck?

Explanation / Answer

calculate the momentum before the puck hits the goalie: momentum = mass*velocity
p = 0.18*64
p = 11.52 kg.m/s

Because the final momentum is zero, the change in momentum is also 11.52, which is also called impulse.

Apply impulse = Force*time
11.52 = 8*10^-3*F
F =1440 N

Therefore the average force exerted is 1440 N

b.) As we said from the previous question the original momentum is 11.52 kg.m/s. However, this time the final momentum is not zero: apply momentum = mass*velocity:

p = 0.18*-64
p = -11.52 kg.m/s

So this time the change in momentum is 11.52-(-11.52) = 23.04 kg.m/s, this is also the impulse.

apply impulse = Force*time
23.04 = 8*10^-3*F
F = 23.04 / 8*10^-3
F = 2880N

So now the average force is 2880N

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