A ball with a mass of #5 kg# moving at #20 m/s# hits a still ball with a mass of #6 kg#. If the first ball stops moving, how fast is the second ball moving?

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Answer 1 · 2016-05-31T19:16:55

#v_2^'=50/3 " "ms#

#m_1=5" "kg#
#v_1=20" "m/s#
#P_1=m_1*v_1" momentum for "m_1=5 kg" before collision"#
#P_1=5*20=100" "kg*m/s#

#m_2=6" "kg#
#v_2=0#
#P_2=m_2*v_2=6*0=0" momentum for "m_2=6 kg" before collision"#

#Sigma P_b=P_1+P_2" total momentum before collision"#

#Sigma P=100+0=100" "kg*m/s#

#Sigma P_b=Sigma P_a" In elastic collisions momentum is conserved"#

#100=m_1*v_1^'+m_2*v_2^'#

#100=5*0+6*v_2^2#

#100=0+6v_2^'#

#v_2^'=100/6=50/3 " "m/s#