Angular Impulse-Momentum Principle - Example Problem 10.7-3
A given electric motor has the two-stage starting torque-time curve shown. The rotating parts of the motor may be modeled as a disk of mass 30 kg and radius 300 mm. If the motor starts from rest, determine the angular velocity of the motor at 7 seconds. A magnetic brake is applied to the motor after it has run for 7 seconds. Determine the average braking torque if it takes the motor 4 seconds to come to rest.
Given:
- m = 30 kg
- r = 300 mm
- To = 15 Nm
- ωo = 0 rad/s
- Δtb = 4 s
- state 1 = motor at rest
- state 2 = when t = 7 s just before the brake is applied
- state 3 = after the brake has brought the motor to rest
- Two-stage torque
- Approximate rotating parts of the motor as a disk
Find:
- ω2
What is the mass moment of inertia of the rotating parts of the motor with respect to the axis of rotation?