Find moment of inertia via torque and acceleration parameter

AI Thread Summary
A constant torque of 4 Nm is applied to an unloaded motor, which reaches a speed of 1717 rpm in 4 seconds. The discussion revolves around calculating the motor's moment of inertia, with confusion regarding the units of inertia being expressed as Nm·s² instead of the expected kg·m². Participants clarify that the moment of inertia can be derived using the relationship between torque, inertia, and angular acceleration. The user expresses frustration over understanding the calculations but ultimately finds clarity on how to approach the problem. The conversation emphasizes the importance of grasping the fundamental equations involved in rotational dynamics.
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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.
 
Physics news on Phys.org
1 N = 1 kg * 1 ms-2

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