What term describes the rate at which velocity changes?

• A. Displacement
• B. Gravity
• C. Field Force
• D. Acceleration

Answer: (D)

Acceleration is the rate at which velocity changes. Because velocity includes both speed and direction, any change in either one constitutes acceleration. If you speed up, slow down, or change direction (even at constant speed, like in circular motion), you’re experiencing acceleration. The average acceleration is the change in velocity divided by the time taken, a = Δv/Δt, and the instantaneous acceleration is the derivative dv/dt. The units are meters per second squared.

Displacement describes how far an object moves, not how its velocity changes. Gravity is a force that causes acceleration, but is not the rate itself. “Field force” isn’t the term used for the rate of change of velocity.