Question

6. Two skaters, Jim (65 kg) and Mary (50 kg) are standing at rest on the ice. They push each other
and Mary recedes at 2.5 m/s towards the east. Find Jim's velocity (magnitude and direction).

Answer 1

Hi there!

This is an example of a recoil collision.

Let m1, v1 be Mary

Let m2, v2 be Jim

Utilize the conservation of momentum:

m1v1 + m2v2 = m1v1' + m2v2'

The initial velocities are zero (at rest), so:

0 = m1v1' + m2v2'

Let east be positive, so Jim recoils with a negative velocity:

0 = m1v1' - m2v2'

Set the two equal and solve:

m1v1' = m2v2'

m1v1'/m2 = v2'

(50)(2.5)/65 = v2' = 1.92 m/s to the WEST