A table fan, rotating at a speed of 2400 rpm, is switched off and the resulting variation of the rpm with time is shown in the figure. The total number of revolutions of the fan before it comes to rest is

Options

A. 420
B. 190
C. 280
D. 380

Answer

C

Explanation

Area under `n-t` graph will give total number of revolution before coming to stop
Area = Total number of revolutions
`=(1)/(2)xx8xx((1800)/(60))+8xx(600)/(60)+(1)/(2)xx16xx((600)/(60))`
`=120+80+80`
`=280`.