An electric fan is turned off, its angular velocity decreases uniformly from 470

Question

An electric fan is turned off, its angular velocity decreases uniformly from 470 rev/min to 160 rev/min in a time interval of length 4.20s
A) Find the angular acceleration in rev/s^2 .
B) Find the number of revolutions made by the motor in the time interval of length 4.20s.
C) How many more seconds are required for the fan to come to rest if the angular acceleration remains constant at the value calculated in part A ? ltem 2 Part A An electric fan is turned off, and its angular velocity decreases uniformly from 470 rev/min to 160 rev/min in a tme interval of length 4 20s Find the angular acceleration in rev/s Submit My Answers Give Up Correct Part B Find the number of revolutions made by the motor in the time interval of length 420 s N 24.08 rev Submit My Answers Give Up Incorrect; Try Again; 2 attempts remaining Part C How many more seconds are required for the fan to come to rest if the angular acceleration remains constant t3.6 Submit Mty Answers Give Up iIncormect Try Again: atepts remaining Incorrect: Try Again; 2 attempts remaining

Explanation / Answer

a) the angular acceleration is

= ( - 0 ) / t

where

then

= ( 2.67 rev/s - 7.83 rev/s ) / ( 4.20 s )

= - 1.23 rev/s2

b) the number of revolution is

= 0 t + ( t2 ) / 2

= 7.83 rev/s * 4.20 s + ( - 1.23 rev/s2 * ( 4.20 s )2 ) / 2

= 22.0 rev

c) the time to stop is

= 0 + t ---> t = ( - 0 ) / a

t = ( 0 rev/s - 7.83 rev/s ) / ( - 1.23 rev/s2 )

t = 6.37 s

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