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Work, Energy, and Power — Physics STD 11 Science — Question

Rajasthan BoardEnglish MediumSTD 11 SciencePhysicsWork, Energy, and Power5 Marks
Question
Two pendulums with identical bobs and lengths are suspended from a common support such that in rest position the two bobs are in contact. One of the bobs is released after being displaced by 10° so that it collides elastically head-on with the other bob.

  1. Describe the motion of two bobs.
  2. Draw a graph showing variation in energy of either pendulum with time, for  where T is the period of each pendulum.
✓

Answer

  1. Let at t = 0 A is at lowest position and B is at its height position at 10°

PEA = 0, PEB = E, KEA = KEB = 0

K.E. of both are zero. Now bob is released.

 reaches to A and collide elastically as both bobs are identical then,

KEA = 0, KEB = E, PEA = 0

PEB = 0

AT  reaches at it’s maximum height and B remains at it’s lowest position.

KEA = 0, KEB = E, PEA = E, PEB = 0

At  Bob A hits the bob B which was at rest elastically and ball A becomes at rest, B moves upward.

KEA = 0, KEB = E, PEA = E, PEB = 0

EA = 0, EB = E

At  Bob B is at its maximum height and A is at lower height.

So, KEA = 0, KEB = 0, PEA = 0, PEB = E

  1. The entire process is repeated.
Time t KEA PEA EA KEB PEB EB
0 0 0 0 0 E E
0 0 E 0 0 0
0 0 0 0 E E
E 0 E 0 0 0
0 0 0 0 E E

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