One ball strikes a wall normally and rebounds with unchanged speed; an identical ball strikes at 30° to the normal and rebounds at 30° with unchanged speed. The ratio of the impulse magnitudes (normal : 30°) is:
A1 : 2
B√3 : 2
C2 : √3
D1 : 1
Answer & Solution
Correct answer: C. 2 : √3
A normal hit reverses momentum fully: impulse = 2mu. At 30° to the normal only the normal component reverses, giving impulse 2mu cos30°. Ratio = 1 : cos30° = 2 : √3 ≈ 1.15.
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