Work, Energy and Power

A body of mass 100 g is moving in circular path of radius 2 m on vertical plane as shown in figure. The velocity of the body at point A is 10 m/s. The ratio of its kinetic energies at point B and C is : [figure] (Take acceleration due to gravity as 10 m/s2)

1. 3- 22
2. 2+ 33
3. 2+ 23
4. 3+ 32

Answer

(4) 3+ 32

Solution

[figure]

Heights above A: hB=R(1- 30 )=2- 3 m, hC=R(1- 120 )=3 m

Energy conservation: v2=vA2-2gh vB2=60+20 3, vC2=100-60=40

KBKC= vB2vC2= 60+20 340= 3+ 32

Answer: (4)