Question

The moment of inertia of a body about a given axis is 1.2kgm^2. Initially, the body at rest. In order to produce a rotational kinetic energy of 1500 joule, an angular acceleration of 25radian/sec^2 must be applied about the axis for duration of ___________

(a) 4s

(b) 2s

(c) 8s

(d) 10s

Answer 1

Correct choice is (b) 2s

The best I can explain: Rotational kinetic energy = 1/2 Iω^2

1500=1/2×1.2×ω^2

ω=√(3000/1.2)=50rad/s

t=(ω-ω0)/α=(50-0)/25

t=2sec.