If you ignore air resistance after an initial force launches a projectile, name all forces acting on it as it moves through the air. What does this force cause the object to do?

Neglecting air resistance, the only force acting on a projectile is gravity.

This force causes the object to accelerate.

Explanation:

As a projectile moves upward, there is a downward force and a downward acceleration due to force of gravity. That is, as the object is moving upward, force of gravity acting on the projectile is causing a steady slowing down of the projectile.

Hence, Gravity is the downward force upon a projectile that influences its vertical motion and causes the parabolic trajectory that is characteristic of projectiles.

From Newton's law of motion, it suggest that force is required to cause an acceleration and not motion. Therefore, force of gravity causes the object to accelerate downwards.