* Work and Force Direction: Work is done when a force acts over a distance. The direction of the force is important. If the force and the displacement are in the same direction, the work is positive. If they are in opposite directions, the work is negative.
* Gravity and Projectile Motion: During the descent of a projectile, gravity acts downwards. The projectile also moves downwards. Therefore, the force of gravity and the displacement of the projectile are in the same direction.
In simpler terms: Gravity is pulling the projectile down, and the projectile is moving down, so gravity is doing work to make that happen. This work is positive because it is increasing the kinetic energy of the projectile as it falls.
