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 figure . How high does the bob A rise after the collision ? Neglect the size of the bobs and assume the collision to be elastic .

Explanation

When ball A reaches bottom oint its velocity is horizontal , hence ,we can use law of conservation of linear momentum in the horizontal direction .
(a) Two balls have same mass and the collision between them is elasti c , therefore , ball A transfers its entire linear momentum to ball B . Hence , ball A will come to at rest after collision .

(b) Speed with which bob B starts moving
= Speed with which bob A hits bob B
` = sqrt(2gh)`
`= sqrt(2xx9.8 xx1)`
` = sqrt(19.6)`
`= 4.42 ` m/s