A ball with a mass of # 5 kg# is rolling at #3 m/s# and elastically collides with a resting ball with a mass of #2 kg#. What are the post-collision velocities of the balls?

1 Answer
Feb 20, 2016

Answer:

#v_1=9/7 m/s#
#v_2=30/7 m/s#

Explanation:

#5*3+0=5*v_1+2*v_2#
#15=5*v_1+2*v_2" (1)"#
#3+v_1=0+v_2" (2)"#
#color(red)"'the sum of the velocities of objects before and after collision must be equal'"#
#"write " v_2=3+v_1" at (1)"#
#15=5*v_1+2*(3+v_1)#
#15=5.v_1+6+2*v_1#
#15-6=7*v_1#
#9=7*v_1#
#v_1=9/7 m/s#
#use :" (2)"#
#3+9/7=v_2#
#v_2=30/7 m/s#