A simple pendulum is oscillating with angular displacement `90^(@)` For what angle with vertical the acceleration of bob direction horizontal?

Explanation

`v =sqrt (2gh) = sqrt(2g1 cos theta) , a_(1) = g sin theta`
`a_(c) = (v^(2))/(l) = 2g cos theta`
Net acceleration will be horizontal if the vertical components of `a_(c) and a_(t)` cancel each other.
For this ,`a_(c) cos theta = a_(t) sin theta`
`rArr 2 g cos^(2) theta = g sin^(2) theta rArr` an `theta = sqrt(2)`