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
