Question

The moment of inertia of a body about a given axis is 1.2 kg × m². Initially, the body is at rest. In order to produce a rotational KE of 1500 joule, an angular acceleration of 25 rad/sec² must be applied about that axis for a duration of –

• A. 4 s
• B. 2 s
• C. 8 s
• D. 10 s

Answer 1

Answer: (B)

2 s

Answer 2

K_R = $\frac { 1 } { 2 }$ Iw² = $\frac { 1 } { 2 }$ I (at)² = $\frac { 1 } { 2 }$ Ia²t²

1500 = $\frac { 1 } { 2 }$ × 1.2 × (25)²t²

or t² = 4 or t = 2s