Hi, I have a physics problem I need to solve which I think is quite straight forward but would appreciate some input on whether I'm going down the right lines Tow metal spheres hanging from the roof one of 10g (ball1) and one of 100g (ball2) ball1 is falling from a height of 15cm accelerating at 9.81ms-2 and collides with sphere b which is stationary After the collision sphere ball2 is moving at a velocity of 1ms What is the velocity of ball1? Now my logic is as follows and I would appreciate comments. To get the velocity of ball1 we need to use the equation v = (Uball1(Mball1- Mball2)+2 x Mball2 x Uball2) / Mball1+Mball2 Now we have everything we need apart from Uball1 Uball1 we need to calculate using Uball1 = sqrt(2x9.81x0.15m) Once I have Uball1 I can calculate the velocity of ball1 after the collision. Is my thinking correct? Thanks for your help.