Carter pushes a bag full of basketball jerseys across the gym floor. The he pushes with a constant force of 21 newtons. If he pushes the bag 9 meters in 3 seconds, how much power does he use? (Hint: 1 watt = 1.)

Power is the rate of work that is done per time. Work is calculated from the product of force and the displacement. So, by using the definition of power and work, we can relate power with force, displacement and the time. We do as follows:

Power = Work / time

Power = Force x displacement / time

Power = 21 N (9 m) / 3 s

Power = 63 J / s = 63 W