A person is standing on a truck moving with a constant velocity of...

The time taken by the truck to travel $58.8 \text{ m}$ is given by:

$t = \dfrac{d}{v} = \dfrac{58.8}{14.7} = 4 \text{ s}$

Since the ball returns to the moving truck, its horizontal displacement relative to the truck is zero. This implies that the horizontal component of the ball's velocity relative to the truck is zero. Thus, the ball is thrown vertically upwards as seen from the truck.

The time of flight of the ball is equal to the time taken by the truck, so $T = 4 \text{ s}$.

Using the formula for the time of flight of a projectile thrown vertically upwards:

$T = \dfrac{2u}{g}$

$4 = \dfrac{2u}{9.8}$

$u = \dfrac{4 \times 9.8}{2} = 19.6 \text{ m/s}$

Therefore, the speed of projection as seen from the truck is $19.6 \text{ m/s}$ upward.