A ball with a mass of #1kg# moving at #5 ms^-1# hits a still ball with a mass of #3 kg#. If the first ball stops moving, how fast is the second ball moving?

1 Answer
David G.
Jan 20, 2016

The final velocity of the #3 kg# mass will be #5/3 ms^-1 or 1.67 ms^-1# because momentum is conserved.

Explanation:

Momentum is conserved, so the total momentum before the collision

#p=m_1v_1+m_2v_2=1*5+3*0=5 kgms^-1#

will be the same as the total momentum after

#p=m_1v_1+m_2v_2#

Therefore #5 = 1*0 + 3*v_2#

Rearranging, #v_2 = 5/3 ms^-1 or 1.67 ms^-1#

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