Friction & Power based Numerical Problem: A factory uses a motor and a cable to drag a 300 kg machine to the proper place on the factory floor. What power must the motor supply to drag the machine at a speed of 0.50 m/s? The coefficient of friction between the machine and the floor is 0.60.
The force applied by the motor, through the cable, is the tension force T.
This force does work on the machine with power P = Tv. [we know the formula: power = force x velocity]
The machine is in equilibrium because the motion is at a constant velocity, hence the tension in the rope balances the friction and is
T = fk = µkmg
The motor’s power output P is
P = Tv = µkmgv = 0.6 x 300 x 9.8 x 0.5 = 882 W
So, the motor must supply 882 W of power. [Answer]
[suggested reading: Friction numerical problems solved worksheet for class 11 & class 12