Novelty stores sell a device called a radiometer (Figure), in which a balanced vane spins rapidly. A

Question:

Novelty stores sell a device called a radiometer (Figure), in which a balanced vane spins rapidly. A card is mounted on each arm of the vane. One side of each card is white and the other is black. Assume that the mass of each card is 2 g, that the light-collecting area for each card is 1 cm2, and that each arm of the vane has a length of 2 cm.

(a) If a 100-W light bulb produces 50 W of electromagnetic energy and the bulb is 50 cm from the radiometer, find the maximum angular acceleration of the vane.

(b) How long will it take for the vane to accelerate to 10 rev/min if it starts from rest and is subject to the maximum angular acceleration at all times?