1. The problem statement, all variables and given/known data A ball A is dropped from the top of a building of height h and simultaneously a ball B is thrown upwards and both balls collide. After the collision the ball A has the double the velocity of ball B Determine the fraction of the building where the balls collide. 2. Relevant equations mA.VA+mB.VB=mA.2V'+mB.V' VA=-g.t VB=Vo-g.t 3. The attempt at a solution I tried with conservation of momentum, conservation of energy, but I can't get rid of the masses, they are always there and can't get them out of the equations, so I can't finish the problem. Is there a special case when an object gets the double of the other's object velocity after a collision? I looked for it but I didn't find anything PS: The answer is a fraction (obviously) but there are only numbers in it, so that's the reason I put it here and not in the Advanced Physics Homework. Thanks in advance.