A washing machine motor is switched off, and its angular speed uniformly decreases from 900 rpm to 300 rpm in 8 seconds. The total number of rotations made by the motor during this interval is :

Step-by-step solution

Initial angular velocity, ₀ = 900 rpm = 900 2 60 = 30 rad/s. Final angular velocity, = 300 rpm = 300 2 60 = 10 rad/s. Time taken, t = 8 s. Using the equation of kinematics for rotational motion, the angular displacement is given by: = ( ₀ + 2 ) t = ( 30 + 10 2 ) 8 = 20 8 = 160 rad. The number of rotations N is given by: N = 2 = 160 2 = 80 Answer: 80