Rotational Motion Question 139

Question: A uniform rod of length L (in between the supports) and mass m is placed on two supports A and B . The rod breaks suddenly at length L/10 from the support B. Find the reaction at support A immediately after the rod breaks.

Options:

A) 940mg

B) 1940mg

C) mg2

D) 920mg

Show Answer

Answer:

Correct Answer: A

Solution:

[a] Torque =τ=910mg(920L)=Iα=m3(910L)2α

α=3g2L

 Acceleration, αCM=α(AC)

aCM=3g2L(9L20)=27g40

 Now, 910mgNA=maCM=m27g40 Or 

NA=940mg



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