Properties Of Solids And Liquids Question 201

Question: A uniform rod of density ρ is placed in a wide tank containing a liquid of density ρ0(ρ0>ρ) . The depth of liquid in the tank is half the length of the rod. The rod is in equilibrium, with its lower end resting on the bottom of the tank. In this position the rod makes an angle θ with the horizontal

Options:

A) sinθ=12ρ0/ρ

B) sinθ=12.ρ0ρ

C) sinθ=ρ/ρ0

D) sinθ=ρ0/ρ

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Answer:

Correct Answer: A

Solution:

Let L = PQ = length of rod \ SP=SQ=L2

Weight of rod, W=Alρg , actingAt point S

And force of buoyancy,FB=Alρ0g , [l = PR]which acts at mid-point of PR.

For rotational equilibrium,

Alρ0g×l2cosθ=ALρg×L2cosθ

therefore l2L2=ρρ0 therefore lL=ρρ0

sinθ=hl=L2l=12ρ0ρ



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