- #1
JamesL
- 33
- 0
Here is the question that's been giving me trouble:
A electric motor can accelerate a ferris wheel of moment of inertia I = 25300 kgm^2 from rest to 11.9 rev/min in 11.5 s. when the motor is turned off, friction causes the wheel to slow down from 11.9 rev/min to 6.33 rev/min in 7.53 s.
Determine the torque generated by the motor to bring the wheel to 11.9 rev/min.
Determine the power needed to maintain a rotational speed of 11.9 rev/min.
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The 2nd part seems fairly straight forward. When i find the torque i use
Power = (torque)(rotational speed).
The rotational speed = 11.9 rev/min = .198333 rev/sec = 1.24617 rad/sec.
So the power should be easy to find.
I assume i can find the change in kinetic energy (and therefore the work) by using the following equation:
The final rotating speed = 6.33 rev/min = .662876 rad/sec
change in K = W = .5(25300)(.662876^2) - .5(25300)(1.24617^2)
= -14086.2 J
Im not sure, however, how to find the torque after this?
Any help would be greatly appreciated!
A electric motor can accelerate a ferris wheel of moment of inertia I = 25300 kgm^2 from rest to 11.9 rev/min in 11.5 s. when the motor is turned off, friction causes the wheel to slow down from 11.9 rev/min to 6.33 rev/min in 7.53 s.
Determine the torque generated by the motor to bring the wheel to 11.9 rev/min.
Determine the power needed to maintain a rotational speed of 11.9 rev/min.
-------------------------------------
The 2nd part seems fairly straight forward. When i find the torque i use
Power = (torque)(rotational speed).
The rotational speed = 11.9 rev/min = .198333 rev/sec = 1.24617 rad/sec.
So the power should be easy to find.
I assume i can find the change in kinetic energy (and therefore the work) by using the following equation:
The final rotating speed = 6.33 rev/min = .662876 rad/sec
change in K = W = .5(25300)(.662876^2) - .5(25300)(1.24617^2)
= -14086.2 J
Im not sure, however, how to find the torque after this?
Any help would be greatly appreciated!