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**1. Homework Statement**

A .30 kg ball with initial velocity of 21i - 1.3j colldes with a wall. The wall exerts a force of -155i N on the ball and its final horizontal component of velocity is -11i m/s.

(a) Find the vertical velocity component.

(b) Find the total change in momentum.

(c) How long was the ball in contact with the wall?

**2. Homework Equations**

change in momentum = impulse = Ft

**3. The Attempt at a Solution**

I think my main problem is im not sure if this is a conservatoin of momentum problem or not - is momentum conserved after the collision with the wall? Im having a hard time relating the 155 N force applied from the wall to the ball.

I know that if I can find the vertical component of velocity after hitting the wall, I can easily find the change in momentum (part b) by:

m (vf - vi) where vf and vi are the overall resultant velocity vectors.

and i know that if i get that i can set it equal to Ft to find the time in contact with the wall (part c) but i cannot figure out part a. can someone please help. thanks.