Power Defined as Rate of Work

Steps:

• Recall the standard physics definition: power is how quickly work is done.
• Examine option A: product of force and work per unit time mixes unrelated terms.
• Examine option B: work per unit time times velocity adds extra factor incorrectly.
• Examine option C: force per unit time times velocity confuses impulse with power.
• Confirm option D matches the core definition directly.

Why D is correct:

• Power is defined as the rate of doing work, given by the formula $P = \frac{W}{t}$, where $W$ is work and $t$ is time.

Why the others are wrong:

• A: Incorrectly combines force with work rate; power isn't force times power.
• B: Work per unit time is already power, multiplying by velocity creates a different quantity like kinetic power flux.
• C: Force per unit time is impulse rate, not power; velocity addition is erroneous.

Final answer: D