CBSE (Science) Class 11CBSE
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# 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 Fig. How High Does the Bob a Rise After the Collision? Neglect the Size of the Bobs and Assume the Collision to Be Elastic - CBSE (Science) Class 11 - Physics

ConceptConcept of Collisions

#### 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 Fig. How high does the bob A rise after the collision? Neglect the size of the bobs and assume the collision to be elastic. #### Solution 1

The bob A will not rise because when two bodies of same mass undergo an elastic collision, their velocities are interchanged. After collision, ball A will come to rest and the ball B would move with the velocity of A, Figure. Thus the bob A will not rise after the collision.

#### Solution 2

Since collision is elastic therefore A would come to rest and B would begin to move with the velocity of A. The bob transfers its entire momentum to the  ball on the table. The bob does not rise at all.

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#### APPEARS IN

NCERT Solution for Physics Textbook for Class 11 (2018 to Current)
Chapter 6: Work, Energy and Power
Q: 17 | Page no. 137
Solution 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 Fig. How High Does the Bob a Rise After the Collision? Neglect the Size of the Bobs and Assume the Collision to Be Elastic Concept: Concept of Collisions.
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