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Question
The bob A of a pendulum released from horizontal to the vertical hits another bob B of the same mass at rest on a table as shown in figure.
If the length of the pendulum is 1 m, calculate
- the height to which bob A will rise after collision.
- the speed with which bob B starts moving. Neglect the size of the bobs and assume the collision to be elastic.
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Solution
a. Two balls have the same mass and the collision between them is elastic, therefore, ball A transfers its entire linear momentum to ball 8. Hence, ball A will come to rest after the collision and does not rise at all.
b. Speed with which bob B starts moving
= Speed with which bob A hits bob B
= `sqrt(2gh)`
= `sqrt(2 xx 9.8 xx 1)`
= `sqrt(19.6)`
= 4.42 m/s
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