What is the magnitude of body B's velocity after the collision?

Question

Body A of mass M has an original velocity of 6.2 m/s in the +x-direction toward a stationary body (body B) of the same mass. After the collision, body A has velocity components of 1.1 m/s in the +x-direction and 2.1 m/s in the +y-direction. What is the magnitude of body B's velocity after the collision?
________m/s

I tried and got 3 but that is not right.. please explain how to do this!

Answer 1

Body A had a momentum of 6.2M in the +x-direction, and a momentum of 0 in the y-direction. After the collision, it has a momentum of 1.1M in the +x-direction and 2.1M in the +y-direction. But the total momentum of the system must have the same momentum as Body A originally had, due to conservation of momentum. Thus, by simple arithmetic, Body B must have a momentum of 5.1M in the +x-direction and 2.1M in the -y-direction, because 1.1M + 5.1M = 6.2M, and 2.1M - 2.1M = 0. Since Body B has mass M, just like Body A, Body B has velocity of 5.1 m/s in the +x-direction and 2.1 m/s in the -y-direction. The magnitude of the velocity is found by using the Pythagorean theorem: sqrt(5.1^2 + 2.1^2) = 5.51 m/s.

Answer 2

1