Body A of mass M has an original velocity of 6.2 m/s in the +x-direction toward a stationary body?

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

Please tell me HOW to do this problem, I tried and got 3 but that is not right.. please explain how to do this!

Answer 1

Momentum must be conserved. Since momentum is a vector both the x component (initially=6.2M) and the y component (initially=0) must remain the same.
A's x,y momentum = 1.1M, 2.1M
Then B's x,y momentum must be (6.2-1.1)M, -2.1M
So B's x,y velocity VB = 5.1, -2.1
Magnitude of VB = sqrt(5.1^2+2.1^2)