A ball with a mass of #7 kg# moving at #4 m/s# hits a still ball with a mass of #21 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?

Question

1272 views around the world

You can reuse this answer
Creative Commons License

Answer 1 · 2017-08-21T09:58:32

The velocity of second ball is #=4/3ms^-1#. The loss of kinetic energy is #=37.33J#

We have conservation of linear momentum

#m_1u_1+m_2u_2=m_1v_1+m_2v_2#

Therefore,

#7*4+21*0=7*0+21*v_2#

#v_2=7*4/21=4/3ms^-1#

Loss of kinetic energy is

#DeltaKE=1/2m_1u_1^2-1/2m_2v_2^2#

#=1/2*7*4^2-1/2*21*4^2/3^2#

#=56-18.67=37.33J#