Hockey players wear protective helmets with facemasks. Why? Because the bone in

Question

Hockey players wear protective helmets with facemasks. Why? Because the bone in the upper part of the cheek (the zygomatic bone) can fracture if the acceleration of a hockey puck due to its interaction with the bone exceeds 900 g for a time lasting 6.0 ms or longer. Suppose a player was not wearing a facemask. Is it likely that the acceleration of a hockey puck when hitting the bone would exceed these numbers? Assume a hockey puck can reach a speed of 50 m/s , it bounces back with almost the same speed after the contact, and the contact time interval is 0.01 s.

Explanation / Answer

Initial velocity u = 50 m/s

Final velocity v = -50 m/s (direction reverses)

a = (v - u)/t

Accelaration a =(-50 -50) / 0.01 = -10000 m/s2

This accelaration is greater than 900g

900 g = 900*9.81 = 8829 m/s2

Interaction time = 0.01 S =10 ms

So the puck increases the specified numbers and will cause fracture.

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