(a) Find the recoil velocity of a 70.0-kg ice hockey goalie, originally at rest, who catches a 0.150-kg hockey puck slapped at him at a velocity of 35.0 m/s.

(b) How much kinetic energy is lost during the collision? Assume friction between the ice and the puck-goalie system is negligible. (See Figure 8.8 )

Strategy 

Momentum is conserved because the net external force on the puck-goalie system is zero. We can thus use conservation of momentum to find the final velocity of the puck and goalie system. Note that the initial velocity of the goalie is zero and that the final velocity of the puck and goalie are the same. Once the final velocity is found, the kinetic energies can be calculated before and after the collision and compared as requested.

Transcribed Image Text:

Before net F = 0 P₁ = Plot m₁ V₁ System of interest S V/₂ = 0 Frictionless ice surface After KE'Int< KE int P₁ + P₂ = Ptot System of interest S V₁ = V₂ = v' Frictionless ice surface