Final answer:
Yes, power expended by a force can be negative when the force exerted on an object and the displacement of the object are in opposite directions, resulting in energy being transferred from the object to the force exerting entity.
Step-by-step explanation:
Can the power expended by a force be negative? The answer is yes, the power expended by a force can indeed be negative. This occurs when the force exerted on an object and the displacement of the object are in opposite directions. In physics, power is defined as the rate at which work is done, which can be calculated as P = F ⋅ v, where P is power, F is force, and v is velocity. If the force and velocity vectors are in opposite directions, the dot product is negative, resulting in negative power. This implies that energy is being transferred from the object to whatever is exerting the force.
For example, if a generator applies an upward force to a briefcase while it is moving downward, this results in negative work done on the briefcase because the force exerted by the generator is in the opposite direction of the briefcase's displacement. Consequently, energy is removed from the briefcase and transferred to the generator.