Which statement correctly defines mechanical power?

• A. The total energy of the system.
• B. The rate at which work is done.
• C. The change in momentum over time.
• D. The distance moved per unit time.

Answer: (B)

Power is the rate at which energy is transferred by doing work. When a force moves an object, the work done equals the energy transferred, and power tells you how quickly that transfer happens. Instantaneous power is P = dW/dt, and for a force along the motion with velocity v, P = F · v. This means pushing harder or moving faster increases the energy transferred per second, raising power. The statement that defines power in this way is the correct one. Energy, on the other hand, is the total amount of stored or transferred energy, not how fast the transfer occurs; momentum change over time is about impulse, and distance moved per unit time describes speed, not power.