Question

Which of the following are true for an object in projectile motion?

Check all that apply.

A. The time it takes the object to reach the ground is not affected by its initial velocity.

B. The object accelerates to Earth at g=9.8 m/s2.

C. The horizontal and vertical motions are independent.

D. The only force acting on the object is gravity.

Answer 1

The correct options are: B, C and D.

In fact:
- B is true, because the motion of the projectile can be decomposed in two independent motions on the x and y axis. On the x-axis, there is no acceleration; while on the y-axis, the projectile is accelerating towards the ground with $g=9.81 m/s^2$ (acceleration of gravity)
- C is true, because the two motions on the horizontal and vertical direction are independent. In particular, the horizontal motion is a uniform motion (constant velocity), while the vertical motion is a uniformly accelerated motion (because of the gravitational acceleration g acting on the projectile)
- D is true, in fact (if we neglect air resistance) gravity is the only force acting on the projectile.