A 2 kg object moving at 3 m/s to the right collides inelastically with a 4 kg object at rest. If they stick together, what is their common velocity after collision?
Show the answer and explanation
Correct answer
B. 1 m/s
Principle or equation
Conservation of momentum: m1 v1 + m2 v2 = (m1 + m2) v_common.
Why this answer is correct
Initial momentum = 2*3 + 4*0 = 6 kg m/s. Total mass = 6 kg. v_common = 6/6 = 1 m/s.
Example
A 1 kg ball at 4 m/s hits a 3 kg stationary ball and they stick; v = (1*4)/(1+3) = 1 m/s.
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