Question

Find the minimum speed at A so that the ball can reach at point B as shown in figure. Also discuss the motion of particle when `T=0`, `v=0` simultaneously at `theta=90^@`

Answer 1

From energy conservation,
`1/2mv_A^2+0=0+mgl`
(for minimum speed, `v_B=0`)
`v_(min)=sqrt(2gl)`
At position B, `v=0` and `T=0`.
Putting `v_B=0` or `theta=90^@`, in (i) ball will return back, motion is oscillatory