A small ball is suspended from point O by a thread of length `l`. A nail is driven into the wall at a distance of `l//2` below O, at A . The ball is drawn aside so that the thread taken up a horizontal position at the level of point O and then released. Find
(a) A what point of the ball's trajectory, will the tension in the thread disappear?
(b) What will be the highest point to which it will rise?

Explanation

To solve the problem step by step, we will break it down into two parts as per the question:

### Part (a): Finding the point where the tension in the thread disappears.

1. **Understanding the Setup**:
- A small ball is suspended from point O by a thread of length \( l \).
- A nail is driven into the wall at point A, which is \( \frac{l}{2} \) below O.
- The ball is drawn aside to a horizontal position and then released.
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