The coefficient of restitution (e) for a direct central impact between two bodies is defined as:
Choose the correct answer
Ratio of impulse forces during impact
Ratio of relative velocity of separation to relative velocity of approach along line of impact (e = v2 - v1) / (u1 - u2)
Ratio of masses of the two bodies
Energy retained after impact / energy before impact
Correct Answer
B. Ratio of relative velocity of separation to relative velocity of approach along line of impact (e = v2 - v1) / (u1 - u2)
Why is this the answer?
e = (v2 - v1)/(u1 - u2), where u = pre-impact velocity, v = post-impact velocity (along line of impact). e = 1: perfectly elastic (no energy loss); e = 0: perfectly plastic (they stick together); 0 < e < 1: real impacts. Energy lost = m1 m2 (1-e^2)(u1-u2)^2 / (2(m1+m2)).
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