Question

A fan rotating with 120 revolutions per minute is switched off. It stops in 10 second. Assuming its angular retardation to be uniform,cal. The no. Of rotations it will make in that time

Answer 1

hope this will help u

Answer 2

Hey dear,

◆ Answer-
10 revolutions

◆ Explaination-
# Given-
ω1 = 120 rpm = 2 Hz
ω2 = 0 Hz
t = 10 s

# Solution-
Using 1st kinematic eqn for rotational motion -
ω2 = ω1 + αt
0 = 2 + 10α
α = -0.2 rad/s^2

Using 2st kinematic eqn for rotational motion -
θ = ω1t + 1/2 αt^2
θ = 2 × 10 + 1/2 × (-0.2) × 10^2
θ = 10

10 revolutions will be done before stopping.

Hope this helps you...