Question

A man of mass of mass 25 kg is standing on a platform of mass 50 kg kept on smooth ice. If the man starts moving on the platform with a speed 20 m/s relative to the platform, with what velocity, relative to the ice, does the platform recoil?

Answer 1

initial momentum = 0 (both the objects are at rest)

f.m of man =25×20

=500kgm/s

f.m of platform =50×v

total f.m =500+50v

According to the law of conservation of momentum,

initial momentum =final momentum

0=500 +50v

50v=-500

v =-500÷50

v =-10m/s

Therefore the platform recoils with a velocity of 10m/s in the direction opposite to the motion of the man.