Problem: "A ball with the mass of .440 kg moving east (+x direction) with a speed of 3.70 m/s collides head-on with a .220 kg ball at rest. If the collision is perfectly elastic, what will be the speed and direction of each object after the collision? Relevant equations. Conservation of momentum: m* vi of b1 + m* vi of b2= m* vf of b1 + m* vi of b2 and conservation of kinetic energy... 1/2mvf^2= 1/2 mvi^2 Attempt at Solution: .440(3.70) + .220(0)= .440(vf1) + .220(vf2) 1.63= .44(vf1) + .220(Vf2) and then... 1/2 (.440)(3.7^2)= 1/2 (.440)(Vf^2) + 1/2(.220)(vf^2) 3.01= " " **** Where do I go from here? Also, do I have to use the component form (as in, momentum of initial x component= momentum of final x component), etc? What about angles? I'm so confused because I feel like I should be using angles if its 2-D collisions, but none are given in the problem and I'm not sure if they'll go off a 90 degree angle or not?