I need help with this. I don't know what equation to use. A 5.5g bullet is fired into a block of wood w/a mass of 22.6g. the wood block is initially at rest on a 1.5m tall post. after the collision, the wood block and bullet land 2.5m from the base of the post. how do you find the initial speed of the bullet? I think that you would use the momentum equation, but I dont understand where the height and displacement come in.