Question

m.c.q . a small bob of mass m is tied to a straing and revolved in a veriticle circular of radius if. its speed at the higst point is r√ 3 rg the lowes point is.........​

Answer 1

Let the velocity at lowest point be v. then according to law of conservation of energy.

energy at lowest point= energy at highest point

⇒21mv2=mg(2r)+21m(3rg)2⇒v=7rg

At lowest point, 

rmv2=T−mg⇒T=mg+rmv2=mg+rm(7rg)2

⇒T=mg+7mg=8mg

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