Manipal Entrance Test 2013 Physics Paper

Kinetic energy of rotation is half the product of the moment of inertia (l) of the body and the square of the angular velocity (ω) of the body.
Kinetic energy of rotation =

1

2

× moment of inertia × angular velocity
i.e., K=

1

2

lω2
ω2=

2K

l

Given l=1.2‌kg‌m2,K=1500J
ω2=

2×1500

1.2

⇒ω=50‌rad∕s
From the equation of angular motion, we have
ω=ωn+αt
where ω0 is initial angular velocity, α is angular acceleration and t is time
given ω0=0
ω=50 rad/s,
α=25 rad/s‌2
t=

ω

α

=

50

25

=2s