A ball with a mass of #2 kg# moving at #8 m/s# hits a still ball with a mass of #9 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

1230 views around the world

You can reuse this answer
Creative Commons License

Answer 1 · 2017-03-22T17:53:40

The velocity of the second ball #=1.78ms^-1#
The kinetic energy lost is #=49.8J#

Momentum is conserved

#m_1u_1+m_2u_2=m_1*v_1+m_2v_2#

#u_2=v_1=0#

#m_1u_1=m_2v_2#

#v_2=m_1/m_2*u_1#

#=2/9*8=16/9=1.78ms^-1#

#KE# before is #=1/2m_1u_1^2=1/2*2*8^2=64J#

#KE# after is #=1/2m_2v_2=1/2*9*1.78^2=14.2J#

Loss in #KE# is #=64-14.2=49.8J#