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?

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Answer 1 · 2016-01-17T11:44:43

Speed = #6.25ms^-1#
Energy lost = 45J

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