A desk fan has three (approximately) rectangular sheets of 15.8 cm long and 5 cm wide, each with a mass of 140 g. The fan is rotating at a constant angular speed of 19.8 rad / s when the power is turned off. Due to friction the angular velocity of the fan slows down in a uniform manner and after 5.2 s it still runs at 4.30 rad / s.

Question

A desk fan has three (approximately) rectangular sheets of 15.8 cm long and 5 cm wide, each with a mass of 140 g. The fan is rotating at a constant angular speed of 19.8 rad / s when the power is turned off. Due to friction the angular velocity of the fan slows down in a uniform manner and after 5.2 s it still runs at 4.30 rad / s.
How many revolutions has the fan performed at this time?

Scott · Answer

{[(19.8 + 4.30) / 2] * 5.2} / π

Bob · Answer

Thx