Ayoung hockey player on frictionless ice shoots a 1 kg hockey puck 150 m/s toward the goal. of the hockey player slides backward at 3m/sec what is his mass?

By conservation of linear amount of movement we have:
 m1v1i + m2v2i = m1v1f + m2v2f
 Where,
 v1i = v2i = 0 (assuming initial rest)
 m1v1f + m2v2f = 0
 Substituting the values:
 m1 (-3) + (1) (150) = 0
 Clearing m1:
 m1 = (- (1) * (150)) / (- 3)
 m1 = 50 Kg
 
 his mass is 50 Kg