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Question
The bob A of a pendulum released from 30° to the vertical hits another bob B of the same mass at rest on a table, as shown in the figure. How high does the bob A rise after the collision? Neglect the size of the bobs and assume the collision to be elastic.
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Solution
When the bob A of a pendulum, released from an angle of 30° to the vertical, collides with another stationary bob B of the the same mass, the collision being elastic, their velocities are exchanged. As a result of this elastic collision, bob A will come to rest immediately after the impact, while bob B will acquire the velocity that bob A had just before the collision. Therefore, after the collision, bob A does not rise again; it remains at rest
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