A ball suspended by a thread swings in a vertical plane so that its acceleration in the extreme position and lowest position are equal. The angle `theta` of thread deflection in the extreme position will be

Explanation

Acceleration at point `A, a_(1) = g sin theta ` at point `B ,a_(2)= (v^(2))/(l)`
where `v = sqrt(2gh) = sqrt(2g(1 - 1 cos theta))`
`rArr a_(2) = 2g (1 - cos theta )`
Given` a_(1) = a_(2) rArr g sin theta = 2g( 1 - cos theta )`
Squaring both sides and solving we get
`cos theta = (3)/(5) rArr theta = 53^(@)`