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Grade 11Mechanics

a smooth rod of 4kg rests on two supports A and B.

From a point c at its centre 9kg is suspended by a string of length 1 m. when θ is 30 deg it is released from rest. find maximum displacement of rod.

ans given is 0.2 m

please explain

Profile image of Gundoos 1234
15 Years agoGrade 11
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1 Answer

Profile image of Pramod J AskiitiansExpert-IIT-B
15 Years ago

Dear student,

Elasticity and area of cross section are required to find the deflection only due to weight.

let x be the initial deflection,

force due to pendulum is maximum when it is at mean position 

=> velocity at mean position is = [2g*l(1-cos(theta)]^1/2

force at mean position = mv^2/l

=> 9*g/1 = 90N

so maximum deflection will be 2x.