One end of a horizontal uniform beam of weight W and length L is hinged on a vertical wall at point O and…

One end of a horizontal uniform beam of weight W and length L is hinged on a vertical wall at point O and its other end is supported by a light inextensible rope. The other end of the rope is fixed at point Q, at a height L above the hinge at point O. A block of weight αW is attached at the point P of the beam, as shown in the figure (not to scale). The rope can sustain a maximum tension of  22W. Which of the following statement(s) is(are) correct?

 

  1. The vertical component of reaction force at O does not depend on α.
  2. The horizontal component of reaction force at O is equal to W for α=0.5.
  3. The tension in the rope is 2W for α=0.5.
  4. The rope breaks if α>1.5.

Solution

 

 Rod is in equilibrium, net torque on the rod about O will be zero.

Wl2+αWl=T2l

W2+αW=T2T=2Wα+0.5   ...1

Now checking options-

(A) Force balance on rod,

Nv+T2=W+αW

Nv=W+αW-W2+αW

Nv=W2

Hence, option (A) is correct.

(B) Write horizontal force equation,

NH=T2NH=Wα+0.5

If α=0.5, then,

NH=W and T=2W

Hence, option (B) is correct.

(D)  Maximum Tension of string =22W

So, to break.

T>22W2Wα+0.5>22Wα>1.5

So, string will break.

option (D) correct.

Asked in: JEE Advanced 2021 (Paper 2)

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