A ball with a mass of 3 kg is rolling at 25 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
Mar 4, 2016

v_1^'=5" " m/s
v=2^'=30" " m/s

Explanation:

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m_1*v_1+0=m_1*v_2^'+m_2*v_2^' " Conversation of momentum"
3*25+0=3*v_1^'+2*v_2^'
75=3*v_1^'+2*v_2^' " "(1)
v_1+v_1^'=v_2+v_2^'" "(2)
25+v_1^'=0+v_2^'" "v_2^'=25+v_1^'" "(3)
75=3*v_1^'+2(25+v_1^')
75=3*v_1^'+50+2v_1^'
75-50=5v_1^' " "25=5v_1^'" "v_1^'=5" " m/s
use (3):
v_2^'=25+5
v=2^'=30" " m/s