Ice-hockey star Wayne Gretzky is skating at 16.7 m/s toward a defender, who in t

Question

Ice-hockey star Wayne Gretzky is skating at 16.7 m/s toward a defender, who in turn is skating at 4.86 m/s toward Gretzky. Gretzky’s weight is 713 N; that of the defender is 918 N. Immediately after the collision, Gretzky is moving at 1.53 m/s in his original direction. You can ignore external horizontal forces applied by the ice to the skaters during the collision. What is the velocity of the defender immediately after the collision?

Give your answer in m/s to the second decimal place.

Hint: Take Gretzky’s initial direction as the positive velocity.

Explanation / Answer

mass of each player: Gretzky mass = 713 / 9.81 = 72.75 kg defender mass = 918 / 9.81 = 93.578 kg use conservation of momentum                             pg + pd = pg' +pd' (72.75)(16.7) + (93.578)(-4.86) = (72.75)(1.53) + 93.578v                  1214.925- 454.78 =111.30 +93.578v                                               v = 6.933 m/s in same direction asgretzky                  mass of each player: Gretzky mass = 713 / 9.81 = 72.75 kg defender mass = 918 / 9.81 = 93.578 kg use conservation of momentum                             pg + pd = pg' +pd' (72.75)(16.7) + (93.578)(-4.86) = (72.75)(1.53) + 93.578v                  1214.925- 454.78 =111.30 +93.578v                                               v = 6.933 m/s in same direction asgretzky                 

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