Ball A, with a mass of 10kg, is moving to the right at 20 m/s. Ball B is moving to the left at 20 m/s. Upon collision, Ball B comes to a standstill, and Ball A moves to the left at twice its original speed. What is the mass of ball B?

Question

How do I do this?

Answer 1

momentum is conserved

right is positive

(10 * 20) - (B * 20) = (B * 0) - (10 * 20)

2(10 * 20) = B * 20