A ball with a mass of #3# #kg# moving at #8# #ms^-1# hits a still ball with a mass of #6# #kg#. If the first ball stops moving, how fast is the second ball moving? How much heat energy was lost in the collision?

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Answer 1 · 2016-06-21T11:16:11

Momentum will be conserved, kinetic energy will not.

Velocity of the #6# #kg# ball after the collision is #4# #ms^-1#.

The energy lost as heat is #96-48=49# #J#.

Total momentum before the collision is #p=mv=3xx8=24# #kgms^-1#.

Total momentum after is the same so, rearranging, #v=p/m=24/6=4# #ms^-1#.

Kinetic energy before the collision is:

#E_k=1/2mv^2=1/2xx3x8^2=96# #J#

Kinetic energy after the collision is:

#E_k=1/2mv^2=1/2xx6x4^2=48# #J#

The energy lost as heat is the difference: #96-48=49# #J#.