Question

A 77.0-kg ice hockey goalie, originally at rest, catches a 0.125-kg hockey puck slapped at him at a velocity of 37.5m/s. Suppose the goalie and the ice puck have an elastic collision and the puck is reflected back in the direction from which it came.What would the final velocities of the goalie and the puck be in this case? Assume that the collision is completely elastic.
A. v goalie = _____ m / s
B. v puck = ______ m / s

Answer 1

Answer

given,

Mass of ice hockey goalie = (M) = 77 Kg

mass of pluck = (m) = 0.125 Kg

velocity of pluck (u₁)= 37.5 m/s

u₂ = 0

Let v₁ and v₂ are the velocity of m₁ and m₂

final velocities are

$v_1 = \dfrac{M-m}{M+m}u_2 + \dfrac{2m}{M+m}u_1$

v_1 is velocity of goalie

$v_2= \dfrac{m-M}{m+M}u_1 + \dfrac{2M}{m+M}u_2$

v_2 is velocity of puck

now,

a) for goalie

$v_1 = \dfrac{M-m}{M+m}u_2 + \dfrac{2m}{M+m}u_1$

$v_1 = \dfrac{77-0.125}{77+0.125}(0) + \dfrac{2(0.170)}{77+0.125}(37.5)$

$v_1 =0.165\ m/s$

b) for pluck

$v_2= \dfrac{m-M}{m+M}u_1 + \dfrac{2M}{m+M}u_2$

$v_2= \dfrac{0.125-77}{77+0.125}(37.5)+ \dfrac{2\times 77}{77+0.125}(0)$

$v_2= -37.38\ m/s$