A ball with a mass of #10# #kg# moving at #6# #ms^-1# hits a still ball with a mass of #12# #kg#. If the first ball stops moving, how fast is the second ball moving?

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Answer 1 · 2016-02-13T22:48:27

#v=5m/s#

#"use conversation of momentum"#
#10*6+0=0+12*v#
#"sum of momentums before event=sum of momentums after event"#
#60=12*v#
#v=60/12#
#v=5m/s#

Answer 2 · 2016-02-13T22:54:37

Total momentum before the collision equals total momentum after the collision. This yields a velocity of #5# #ms^-1# for the second ball.

Let's call the #10# #kg# ball Ball 1 and the #12# #kg# ball Ball 2. We are trying to find #v_2#, the velocity of Ball 2 after the collision.

Total momentum before the collision:

#p_"init"=m_1v_1+m_2v_2=10*6+12*0=60# #kgms^-1#

This will be equal to the total final momentum:

#p_"final"=m_1v_1+m_2v_2=10*0+12*v_2=60# #kgms^-1#

Rearranging:

#12*v_2=60 to v_2 =60/12=5# #ms^-1#