Question

A flywheel rotates with a uniform angular acceleration. Its angular velocity increases from `20pi rad//s` to `40pi rad //s` in 10 seconds. How many rotations did it make in this period ?
A. 80
B. 100
C. 120
D. 150

Answer 1

Correct Answer - D
`alpha=(40pi-20pi)/(10)rad//sec^(2)`
`=2pirad//sec^(2)`
`omega_(2)^(2)=omega_(1)^(2)+2alphatheta`
`((40pi)^(2)=(20pi)^(2))+2(2pi)theta`
`theta=((40pi)^(2)-(20pi)^(2))/(4pi)=(60pixx20pi)/(4pi)=300pi`
`2pi n =300pi`
`n=150.`