Question

The tub of a washing machine goes into its spin cycle, starting from rest and gaining angular speed steadily for 8.00 s, at which time it is turning at 5.00 rev/s. At this point, the lid of the washing machine is opened, and a safety switch turns it off. The tub then smoothly slows to rest in 12.0 s. Through how many revolutions does the tub rotate while it is in motion?

Answer 1

Answer:

N = 50 rev

Explanation:

Initially tub is at rest and then accelerated uniformly to its final speed

so we have

$\omega_i = 0$

$\omega_f = 5 rev/s$

time taken by it to reach the final speed

t = 8 second

now the total number of revolutions is given as

$N = (\frac{(\omega_f + \omega_i}{2})(time)$

now we have

$N_1 = (\frac{0 + 5}{2})(8) = 20 rev$

Now when its lid is opened its safety switch is off due to which it is uniformly decelerated and comes to rest in 12 s

so we have

$N_2 = (\frac{5 + 0}{2})(12)$

$N_2 = 30 rev$

So here we have total number of revolutions given as

$N = 20 + 30 = 50 rev$