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UPSC Civil Service Exam Questions - Engineering

Q1:

A hollow cylinder made of wood (sp. gr. = 0.8) has an external diameter of 1.0 m and an interal diameter of 0.6 m. It floats in water with its axis vertical and is in stable equilibrium. This is possible only when the length of the cylinder is equal to or less than

A 0.72 m

B 0.95 m

C 1.03 m

D 1.20 m

ANS:C - 1.03 m

First wt of log =water of water displaced then we get 0.8l=h.

Here l and h is the total and submerged length of the log in water then distance between CB.
Aand CG(BM)=0.Then calculate I/V here I =MOI and V=submerged volume.
then I/V -BM >0 for a stable condition.
then l < or equal to 1.03 m.