Find moment of inertia via torque and acceleration parameter

  • Thread starter D.B0004
  • Start date
  • #1
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Homework Statement


2-1. A constant torque of 4 Nm is applied to an unloaded motor at rest at time t = 0. The motor reaches a speed of 1717 rpm in 4 s. Assuming the damping to be negligible, calculate the motor inertia in Nm·s2.

Homework Equations


T = J(eff) * dw/dt
J = kg*M^2

The Attempt at a Solution


I have NO clue where to start. First question - why is the motor inertia units stated as Nm*S2? I thought moment of inertia was only kg*m^2 (m = meters).
Second question - can someone point me in the right direction? I have been reading for hours. I know this is simple I'm just missing a link. Thanks for the help.
Also the problem seems basic but I posted it in this section because its for a 4000 level course - Electric Drives. Let me know if it should be elsewhere.
 

Answers and Replies

  • #2
rock.freak667
Homework Helper
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1 N = 1 kg * 1 ms-2

In your first relevant equation, how would you calculate dw/dt?
 
  • #3
17
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Wow. I feel like an idiot. Got it. Thanks.
 

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