First off let me say Im completely stumped. I dont remember teacher teaching this, and its definitely not in book(I went through it 3 or 4 times) and its not even the same book mastering physics uses... The Question is : What is the final angle that the ball's velocity vector makes with the negative y axis? The Given are: A ball of mass m moving with velocity v_i strikes a vertical wall. The angle between the ball's initial velocity vector and the wall is theta_i. The duration of the collision between the ball and the wall is Deltat, and this collision is completely elastic. Friction is negligible, so the ball does not start spinning. In this idealized collision, the force exerted on the ball by the wall is parallel to the x axis. an image cna be found here: http://session.masteringphysics.com/problemAsset/1010992/25/MLM_e2.jpg I have no clue on how to solve this... all I do know however is that physics is not my subject heh. Can anyone help lead me in right direction? (keep in mind I am seriously not good in physics [Math yes] physics no so try and keep it dumb if you can? I want to know how to get the answer..well I have to know actually Edit: Ok I know this much I have to find the Y component and X component and stick them together thing is... how? I was thiking it has to be sin(Theta_i) to get the piece that is rquired for the distance the ball is from the wall?