Physics and the Olympics

Question

Two skaters in a winter Olympic figure skating competition start from rest, push off against each other on a frictionless level ice. One is a man with mass M₁ = 75.6 kg and the other is a woman with mass M₂ = 51.2 kg. If the woman moves away with a speed of 3.87 m/s along the +x-axis direction, what is the velocity of the man?

Answer 1

The resulting momenta must be equal in magnitude but opposite in direction. Using subscript 1 for the man and 2 for the woman,

M₁v₁ = -M₂v₂

v₁ = -(M₂/M₁)v₂

You have M₁, M₂, and v₂. Plug in the numbers and get v₁. The negative sign in the answer means that the man moves in the negative x direction. Now try solving a similar problem that you posted, using this same reasoning.