Question

A young 34-kg ice hockey goalie, originally at rest, catches a 0.145-kg hockey puck slapped at him at a speed of 34.5 m/s. In this problem, take the original direction of the puck as positive. show answer Incorrect Answer 50% Part (a) 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 velocity of the puck, in meters per second, be in this case?

Answer 1

The concept that we need to give solution to this problem is collision equation given by momentum conservation,

Our values are,

$m_2 = 0.145 kg\\u_2 = 34.5 m/s\\m_1 = 34 kg\\u_1 = 0$

Then,

Part A) We can here note that the velocity for the puck is zero (there is not a velocity in that direction)

$V_{goalie} = \frac{m_1-m_2}{m_1+m_2}V_{01} + \frac{2m_2}{m_1+m_2}V_{02}$

$V_{goalie} = \frac{34-0.145}{34+0.145}(0)+\frac{2*0.145}{34+0.145}(34.5)$

$V_{goalie} = 0.2930m/s$

Part B ) We apply the same solution but know we note that in the collision for the Goalie the velocity is zero.

$V_{puck} = \frac{m_1-m_2}{m_1+m_2}V_{02} + \frac{2m_2}{m_1+m_2}V_{01}$

$V_{puck} = \frac{34-0.145}{34+0.145}(34.5)+\frac{2*0.145}{34+0.145}(0)$

$V_{puck} = 34.20m/s$