Question

Starting from rest, two skaters "push off" against each other on smooth level ice, where friction is negligible. One is a woman and one is a man. The woman moves away with a velocity of +2.7 m/s relative to the ice. The mass of the woman is 50 kg, and the mass of the man is 81 kg. Assuming that the speed of light is 4.4 m/s, so that the relativistic momentum must be used, find the recoil velocity of the man relative to the ice.

Answer 1

The initial velocity of both man and women is zero (because starting from rest). Therefore, the initial momentum of the system is zero.

Now both push each other and moves in the different direction, that is why the velocity of man is called as recoil velocity because the man recoil after being pushed.

In the absence of external force, the linear momentum of the system remain conserved.

i.e,

Initial momentum = final momrntum

0 = (50)(2.7) + (81) V

81 V = - 135

V = - 1.67 m/s