What term describes the motion of an object when the only force acting is gravity?

• A. Projectile Motion
• B. Displacement
• C. Gravity
• D. Free Fall

Answer: (D)

Free fall describes motion when gravity is the only force acting on the object. In this situation the acceleration is constant and downward, about g, so the object speeds up as it falls. If you release something from rest, its vertical position changes as y = y0 + v0 t − ½ g t^2 and its speed increases linearly with time, v = v0 − g t (downward). If there is an initial horizontal velocity, gravity still acts downward, and the path becomes a curved, parabolic trajectory, but gravity remains the sole force.

That’s why this term is the best fit: it specifically emphasizes motion caused only by gravity, without other forces like drag. Projectile motion also involves gravity, but it usually refers to motion with an initial velocity that creates a curved path; the phrase described in the question points to the scenario of motion under gravity alone, i.e., free fall. Displacement is just a description of change in position, not the type of motion, and gravity is the force, not the motion itself.