A force acting on an object over a distance defines which physical quantity?

• A. Power
• B. Force
• C. Work (w)
• D. Momentum

Answer: (C)

Work is the amount of energy transferred to or from an object when a force acts on it through a distance. If the force is constant and aligned with the direction of motion, the work done is simply F times the displacement. More generally, work equals the integral of F·dr, so only the component of the force along the actual displacement contributes. This means work can be positive if the force helps the motion, negative if it opposes it, or zero if the force is perpendicular to the motion. The unit is the joule (Newton-meter). This concept directly describes how a force acting over a distance transfers energy; power would talk about how fast this transfer occurs, momentum concerns the state of motion, and force is the cause of motion rather than the quantity defined by acting over a distance.