A ball with a mass of #14 kg# moving at #2 m/s# hits a still ball with a mass of #20 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 · 2018-05-23T08:38:52

Please see the explanation below

#m_1u_1+m_2u_2=m_1v_1+m_2v_2#

The mass the first ball is #m_1=14kg#

The velocity of the first ball before the collision is #u_1=2ms^-1#

The mass of the second ball is #m_2=20kg#

The velocity of the second ball before the collision is #u_2=0ms^-1#

The velocity of the first ball after the collision is #v_1=0ms^-1#

Therefore,

#14*2+20*0=14*0+20*v_2#

#20v_2=28#

#v_2=28/20=1.4ms^-1#

The velocity of the second ball after the collision is #v_2=1.4ms^-1#

The loss in kinetic energy is

#DeltaKE=KE_i-KE_f#

#=1/2*14*2^2-1/2*20*1.4^2#

#=28-19.6#

#=8.4J#

The kinetic energy lost in the collision is #=8.4J#