A warm hockey puck has a coefficient of restitution of 0.50, while a frozen hock

Question

A warm hockey puck has a coefficient of restitution of 0.50, while a frozen hockey puck has a coefficient of restitution of only 0.35. In the NHL, the pucks to be used in games are kept frozen. During a game, the referee retrieves a puck from the cooler to restart play but is told by the equipment manager that several warm pucks were just put into the cooler. To check to make sure he has a game-ready puck, the referee drops the puck on its side from a height of 2 m. How high should the puck bounce if it is a frozen puck?

Explanation / Answer

GIVEN
FOR THE FROZEN PUCK, COEFFICIENT OF RESTITUTION
e = 0.35
hence
initial height h = 2m
hence initial speed of puck while striking theground = u
2*g*h = u2
u = sqroot(2gh)

final height h'
final speed just after puck collisdes with the floor = v
hence
v = sqroot(2gh')

now, from definitoin of coefficnet of restitution
v/u = e
sqroot(h'/h) = e
h' = e^2*h = 0.245

hence the frozen puck should bounce back upto 0.245 m only

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