# Find moment of inertia via torque and acceleration parameter

#### D.B0004

1. 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.

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

3. 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.

Related Introductory Physics Homework Help News on Phys.org

#### rock.freak667

Homework Helper
1 N = 1 kg * 1 ms-2

In your first relevant equation, how would you calculate dw/dt?

#### D.B0004

Wow. I feel like an idiot. Got it. Thanks.

"Find moment of inertia via torque and acceleration parameter"

### Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving