A wheel rotating at an angular speed of 20 rad/s is brought to rest by...
Given:
- Angular speed of the wheel, ω = 20 rad/s
- Time taken to bring the wheel to rest, t = 4.0 s
- Moment of inertia of the wheel, I = 0.20
To Find:
- Work done by the torque in the first two seconds, W(0-2)
Explanation:The formula for the torque required to bring the wheel to rest from an angular speed ω is given by:
τ = Iα
where τ is the torque, I is the moment of inertia of the wheel, and α is the angular acceleration of the wheel.
The formula for angular acceleration is given by:
α = (ω - ω0)/t
where ω0 is the initial angular speed, which is 20 rad/s in this case.
Substituting the values in the above formulas, we get:
α = (20 - 0)/4.0 = 5 rad/s²
τ = Iα = 0.20 × 5 = 1 Nm
The work done by the torque in the first two seconds is given by:
W(0-2) = τθ
where θ is the angle rotated by the wheel in the first two seconds.
The formula for the angle rotated by the wheel is given by:
θ = ω0t + (1/2)αt²
Substituting the values in the above formula, we get:
θ = 20 × 2 + (1/2) × 5 × (2)² = 30 rad
Substituting the values in the formula for work done, we get:
W(0-2) = 1 × 30 = 30 J
Therefore, the work done by the torque in the first two seconds is 30 J.
Answer: The work done by the torque in the first two seconds is 30 J.