The moment of inertia of the body about an axis is 1.2 kg `m^(2)`. Initially the body is at rest. In order to produce a rotational kinetic energy of 1500J, an angualr acceleration of 25 `rad/s^(2)` must be applied about the axis for the duration of

Options

A. 4 s
B. 2 s
C. 8 s
D. 10 s

Answer

B

Explanation

As `l=1.2kg-m^(2), E_(r)=1500J, alpha ="25 rad s"^(-2), omega_(1)=0, t=?`
`"Now, "E_(r)=(1)/(2)l omega^(2)`
`rArr" "omega=sqrt((2E_(r))/(l))=sqrt((2xx1500)/(1.2))="50 rad s"^(-1)`
`"From, "omega_(2)=omega_(1)+ alpha t`
`50=0+25t rArr t=2s`