CGPET 2016 Solved Paper

The bob is moving in a vertical plane, so at highest point velocity must be

v=√5‌gr
=√5gL ...(I)
From Equation,
v2=u2=2‌gh ...(ii)
(

v

2

)2=v2−2‌gh

v2

4

=v2−2‌gh
h=L(1−cos‌θ) ....(iii)
Solving Eqs. (i), (ii) and (iii), we get
cos‌θ=−

7

8

θ=cos−1(

7

8

)≃151°
∴

3π

4

<θ<π must be correct.