Question

*5. A fan is rotating at 90 rpm. When switched off, it
stops after 21 revolutions. Assuming a constant
frictional torque, calculate the time taken by it to
come to a stop.
(2 marks) (Ans. 28 s)​

Answer 1

Answer:

ans 28

Explanation:

hope it will hlp to you

Answer 2

Explanation:

Explanation:

n0 = 90rpm 1.5rps

∴ ω = 2pi n0 = 3pi rad/s

The angle through which the blades of the fan move while

the blades of the fan move while stopping is theta = 2piN = 2pi(21) = 42 pi rad, ω = 0 (fan stops).

Using eyuations analoguos to kinematical equations of motion

α = ω - ω0/t = ω^2 - ω0^2/2theta

∴0-3pi/t = 0-(3pi)^2/2(42pi)

∴t = 28s.