TASC Physical Science Practice Exam

Negative work occurs when the force is opposite the direction of displacement.

The force and displacement are in opposite directions The force and displacement are in the same direction There is no force There is no displacement

Correct Answer:

The force and displacement are in opposite directions

Explanation:

Work is the energy transferred to or from an object as it moves under a force. The key is how much of the force actually acts along the direction of the displacement. When the force points opposite to the motion, the force resists the movement, so energy is taken away from the object and the work is negative. This can be seen from W = F · d = |F||d| cos(theta): with theta = 180 degrees (force opposite to displacement), cos(theta) = -1, giving negative work. Negative work means the object's kinetic energy decreases (often turning into heat). If the force and displacement align, the work is positive and adds energy to the object. If there’s no force or no movement, the work is zero.

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