Which concept describes the product of force and distance moved in the direction of the force?

• A. Friction
• B. Normal Force
• C. Power
• D. Work

Answer: (D)

Work is the transfer of energy that occurs when a force acts on an object as it moves through a distance in the direction of that force. The amount of work is given by W = F · d = F d cos θ, where θ is the angle between the force and the displacement. If the force points the same way as the motion, the work is positive; if it points opposite, the work is negative; if the force is perpendicular to the motion, the work is zero.

So the phrase “product of force and distance moved in the direction of the force” is exactly the definition of work. For example, pushing a 5 N block 2 m in the same direction adds 10 joules of energy to the block (positive work).

Power, on the other hand, is how fast that work is done (P = W/t). Friction is a force that can do work (often removing energy as heat) but the statement describes work in general, not a specific force. Normal force usually does no work in straightforward horizontal sliding because it acts perpendicular to the displacement.