Answer
See work.
Work Step by Step
a. “Strong” refers to the amount of force that the person can apply, but “power” in physics means the rate at which work is done. A large force doesn’t necessarily do much work, or do that work in a short time interval, so “strong” and “powerful” are not interchangeable terms to a physicist.
b. When a worker carries a bag of concrete along a level construction site at constant speed, the worker’s hand’s force and gravity are both perpendicular to the horizontal displacement, and neither force does any work. The net work is zero because the change in kinetic energy is zero.
