Aceiling fan is turned on and reaches an angular speed of 120 rev/min in 20 s. it is then turned off and coasts to a stop in an additional 40 s. the ratio of the average angular acceleration for the first 20 s to that for the last 40 s is which of the following?

a.2
b.-0.5
c.0.5
d.-2

option D

Explanation:

given,

angular speed of the fan = 120 rev/min

time = 20 sec

After 40 s fan comes to rest

ration angular acceleration of the first 20 s to last 40 s.

angular acceleration for first 20 s

for last 40 s

now, ratio

hence, the correct answer is option D

because if the tool that you are using is not balanced it there would be false mass.