A young hockey player stands at rest on the ice holding a 1.3-kg helmet. The player tosses the helmet directly in front of him with a speed of 6.0 m/s and recoils with a speed of 0.25 m/s.

Answer

given,

initial speed of hockey player = 0 m/s

mass of the helmet, m = 1.3 Kg

initial speed of the helmet, u = 0 m/s

final speed of the helmet, v = 6 m/s

recoil speed of the hockey player, v' = 0.25 m/s

we need to calculate the mass of the hockey player, M = ?

using conservation of momentum

m u + M u' = M v' + m v

initial speed of ice skater is zero

1.3 x 0 + M x 0 = M x (-0.25) + 1.3 x 6

negative sign is taken because recoil velocity is in opposite direction

0 = - 0.25 M + 7.8

0.25 M = 7.8

M = 31.2 Kg

Hence, the mass of the young hockey player is equal to 31.2 Kg