A ball with a mass of #15 kg# moving at #4 m/s# hits a still ball with a mass of #24 kg#. If the first ball stops moving, how fast is the second ball moving? How much kinetic energy was lost as heat in the collision? Physics Momentum and Collisions Conservation of Momentum 1 Answer moutar Jan 17, 2016 Answer: Speed = #6.25ms^-1# Energy lost = 45J Explanation: Momentum is conserved so: Momentum before = momentum after #15 * 4 = 24 * v# #v=60/24=2.5ms^-1# Kinetic energy = #1/2mv^2# KE Before = #1/2*15*4^2=120J# KE After = #1/2*24*2.5^2=12*6.25=75J# Energy lost = 120-75=45J Related questions Why does Newton's cradle stop? How does the conservation of momentum apply in rotational motion? How does the conservation of angular momentum effect the stability of a bike? What is the law of conservation of momentum? What is conservation of angular momentum? What is an inelastic collision? What are some examples of an elastic collision? What is an elastic collision? What is the conservation of momentum? A fly splats on your windshield. What is the collision type? See all questions in Conservation of Momentum Impact of this question 153 views around the world You can reuse this answer Creative Commons License