Question

A nail is located at a certain distance vertically below the point of suspension of a simple pendulum of length 1m. The pendulum is released from the horizontal position. If it rotates in a vertical circle with nail as centre, the distiance of nail from point of suspension is

Answer 1

the answer is- 

conversion of P.E. of pendulum bob at  A into K.E. AT L'

1/2mv²L=mgh=mg(L−SB)=mg(L−Lcos θ ) 
or 
v²L=2gL(1−cos θ )
or 
5gr=2gL(1−cos θ ) 
or
 r=25×(1−cos60)=15=0.2 
so, 
 y=L−r=1−0.2=0.8m
If it rotates in a vertical circle with nail as centre, the distiance of nail from point of suspension is 0.8 m

Answer 2

Answer:

0.8

Explanation:

the ANSWER IS 0.8

1/2MV^2=MGH=MG(L-SB)

V^2=2GL(1-COSTHETA)

Y=1-R=1-0.2=0.8