how do you solve this questions

Question

A tennis ball is traveling to the left with a momentum of 3 kg-m/s when it strike a wall and rebounds after the collision with an equal momentum in the opposite direction (to the right) What was the impulse applied to the ball by the wall?

 

 

Just before contact with the bat, a baseball has a momentum of 3 kg-m/s. After the interaction between the bat and ball, the ball leaves the bat with a moment of -2 kg m/s. What is the impulse applied to the ball during its contact with the bat?

Answer 1

Hi Nicole,

Both problems are solved essentially the same way.  The key to the solution is the Impulse-Momentum equation:  Impulse = ΔMomentum

 

In the first problem, the ball's momentum is 3 kg m/s to the left.  It then strikes the wall and leaves with a momentum of 3 kg m/s to the right.  If we define the right as the positive direction, the change in momentum is the difference in the final momentum and initial momentum, or  3 - (-3) = 6 kg m/s.

 

In the second problem, we once again find the difference in momentum.  -2 - 3 = -5 kg m/s.  

 

Hope this helps.

:)