A particle of mass m is shot from ground level at initial speed u and initial angle `theta` relative to the horizontal. When it reaches its highest point in its flight over the level ground, what are the magnitudes of (a) the torque acting on it from the gravitational force and (b) its angular momentum, both measured about the launch point?

Explanation

To solve the problem, we need to find the magnitudes of (a) the torque acting on the particle from the gravitational force and (b) its angular momentum, both measured about the launch point when the particle reaches its highest point in its flight.

### Step 1: Determine the position vector at the highest point
When the particle reaches its highest point, its horizontal displacement \(x\) can be expressed as:
\[ x = \frac{u^2 \sin 2\theta}{2g} \]
The vertical displacement \(y\) at the highest point is given by:
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