A ball with a mass of #12 kg# moving at #7 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 · 2017-05-02T16:01:42

#v_f= 3.5 m/s#
KE lost = #147J#

By conservation of momentum:
#p_i = p_f#
#(12)(7) = (24)(v_f)#
#v_f = 84/24 = 3.5m/s#

By conservation of energy:
#KE_i = KE_f + # heat energy lost
#1/2 (12)(7)^2 = 1/2 (24)(3.5)^2 + KE_(lost)#
#294 = 147 + KE_(lost)#
#KE_(lost) = 147J#