# Worksheet: Work and Power for Rotational Motion

In this worksheet, we will practice applying the work–energy theorem and principle of energy conservation using the quantities associated with rotational motion.

**Q2: **

A uniform cylindrical grindstone has a mass of 10 kg and a radius of 12 cm.

What is the rotational kinetic energy of the grindstone when it is rotating at rpm?

After the grindstone’s motor is turned off, a knife blade is pressed against the outer edge of the grindstone with a perpendicular force of 5.0 N. The coefficient of kinetic friction between the grindstone and the blade is 0.80. Use the work energy theorem to determine how many turns the grindstone makes before it stops.

**Q5: **

A clay cylinder of radius 10.0 cm on a potter’s wheel spins at a constant rate of 30.0 rev/s. The potter applies a force of 12 N to the clay with his hands and the coefficient of friction is 0.15 between his hands and the clay.

What is the power that the potter has to deliver to the wheel to keep it rotating at this constant rate?

**Q8: **

A string wrapped around a pulley is pulled by a constant force
of
50 N directed
vertically downward, as shown in the diagram. The pulley’s radius and its
moment of inertia is kg⋅m^{2}. The
string does not slip as it is pulled. Starting from rest, what is the angular speed
of the pulley after 1.0 m of
string has been unwound from it?