Power is the rate of doing work; which expression equals power?

Power is the rate of doing work; which expression equals power?

• A. Work divided by time
• B. Force times velocity
• C. Mass times acceleration
• D. Distance divided by time

Answer: (A)

Power is the rate at which work is done, so it equals work divided by the time over which the work is done. This is the definition of average power: doing the same amount of work in a shorter time increases power. At a given moment, instantaneous power can also be expressed as P = F · v, since the rate of doing work is the force applied in the direction of the motion multiplied by the velocity. The distance divided by time gives velocity, not power, and mass times acceleration gives force, not power. So the expression that directly equals power is work divided by time.

Power is the rate at which work is done, so it equals work divided by the time over which the work is done. This is the definition of average power: doing the same amount of work in a shorter time increases power. At a given moment, instantaneous power can also be expressed as P = F · v, since the rate of doing work is the force applied in the direction of the motion multiplied by the velocity. The distance divided by time gives velocity, not power, and mass times acceleration gives force, not power. So the expression that directly equals power is work divided by time.