For a movie scene, a 75-kg stuntman drops from a tree onto a 50-kg sled that is moving on a frozen lake with a velocity of 10 m/s toward the shore. (a) what is the speed of the sled after the stuntman is on board?

Given:

m1 = 75 kg

u1 = 0.0 m/s

m2 = 50 kg

u1 = 10 m/s

Conservation of momentum, velocity of combined system from individual objects

v * [m1+m2] = m1u1 + m2u2

v * [ (75 kg) + (50 kg) ] = [ (75 kg) * (0.0 m/s) ] + [ (50 kg) * (10 m/s) ]

v * [ 125 kg ] = [ 500 kg-m/s ]

v = [ 500 kg-m/s ] / [ 125 kg ]

v = 4 m/s

the speed of the sled after the stuntman is on board is 4 m/s