Find moment of inertia via torque and acceleration parameter

In summary, the problem involves a motor with a constant torque of 4 Nm applied at rest, reaching a speed of 1717 rpm in 4 seconds. To calculate the motor's inertia, we can use the equation T=J(eff)*dw/dt, where J represents the motor's inertia and dw/dt is the angular acceleration. The units for J are typically kg*m^2, but in this problem, it is given in Nm*s^2. To solve the problem, we need to first calculate dw/dt, which can be found using the given information.
  • #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.
 
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  • #2
1 N = 1 kg * 1 ms-2

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

What is the moment of inertia?

The moment of inertia is a physical quantity that measures an object's resistance to rotational motion. It is also known as rotational inertia.

How is the moment of inertia calculated?

The moment of inertia can be calculated by multiplying the mass of an object by the square of its distance from the axis of rotation. This calculation can be simplified using the parallel axis theorem for objects with non-uniform density.

What is the relationship between torque and moment of inertia?

Torque is directly proportional to the moment of inertia and angular acceleration, and follows the equation τ = Iα, where τ is the torque, I is the moment of inertia, and α is the angular acceleration. This means that a larger moment of inertia will require a larger torque to produce the same angular acceleration.

How can I use torque and acceleration to find the moment of inertia?

The moment of inertia can be found by measuring the torque applied to an object and the resulting angular acceleration, and using the equation τ = Iα to solve for I. This method is often used in experiments involving rotational motion.

Why is the moment of inertia an important concept in physics?

The moment of inertia is an important concept in physics because it helps us understand how objects behave when rotating, such as how much force is needed to change their rotational motion or how they distribute their mass around an axis. It is also used in many engineering and design applications, such as in the design of vehicles and machinery.

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