Inertia Question: Resolve the Wheel Motion

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Homework Help Overview

The discussion revolves around a problem involving a full metal wheel with a specified radius and mass, focusing on calculating various parameters such as angular acceleration, angular speed, revolutions per second, total revolutions, and kinetic energy. The problem is situated within the context of rotational dynamics and involves the application of relevant equations of motion and energy.

Discussion Character

  • Mixed

Approaches and Questions Raised

  • Participants discuss the application of formulas for angular velocity and kinetic energy, with some expressing confusion about the units of kinetic energy obtained in their calculations. There is an exploration of the relationship between torque, angular acceleration, and the resulting energy values.

Discussion Status

Some participants have provided calculations and results, while others question the accuracy of these results. There is an ongoing dialogue about the interpretation of the problem and the correctness of the calculations presented. The discussion reflects a mix of attempts to clarify misunderstandings and verify numerical outcomes.

Contextual Notes

Participants note that the torque is applied for a duration of one minute, which is a point of confusion regarding its relevance to the calculations of angular motion. There is also a mention of the potential misinterpretation of the time variable in relation to the problem's requirements.

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Homework Statement



The full metal wheel of radius 30 cm, 300 kg of mass moment of inertia I = 1/2 (mr ^ 2) operating torque 50nm in time 1 min. Determine the angular acceleration, angular speed of wheel, revolutions per second, revolutions that the wheel makes to achieve this speed, kinetic energy.

Homework Equations



ω = 2∏/T, s=1/2(αt^2), Ek=(Iω^2)/2, I = 1/2 (mr ^ 2)

The Attempt at a Solution



First I can get ω, T=60sec, so ω=∏/30...

So I can get all of this using those few formulas, but in the end I get kinetic energy in mJ??
 
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the_man said:

Homework Statement



The full metal wheel of radius 30 cm, 300 kg of mass moment of inertia I = 1/2 (mr ^ 2) operating torque 50nm in time 1 min. Determine the angular acceleration, angular speed of wheel, revolutions per second, revolutions that the wheel makes to achieve this speed, kinetic energy.

Homework Equations



ω = 2∏/T, s=1/2(αt^2), Ek=(Iω^2)/2, I = 1/2 (mr ^ 2)

The Attempt at a Solution



First I can get ω, T=60sec, so ω=∏/30...

So I can get all of this using those few formulas, but in the end I get kinetic energy in mJ??
Why not get kinetic energy in Joules ?
 
SammyS said:
Why not get kinetic energy in Joules ?

I can get energy in Jules but then its very small number, but i don't get it why is a small number?
 
the_man said:

Homework Statement



The full metal wheel of radius 30 cm, 300 kg of mass moment of inertia I = 1/2 (mr ^ 2) operating torque 50nm in time 1 min. Determine the angular acceleration, angular speed of wheel, revolutions per second, revolutions that the wheel makes to achieve this speed, kinetic energy.

Homework Equations



ω = 2∏/T, s=1/2(αt^2), Ek=(Iω^2)/2, I = 1/2 (mr ^ 2)

The Attempt at a Solution



First I can get ω, T=60sec, so ω=∏/30...

So I can get all of this using those few formulas, but in the end I get kinetic energy in mJ??

The torque is acting for 1 minute; The given time of 1 minute is not the period of oscillation or rotation...
 
Okay. I got it! Now its Ek=7,5kJ
 
Perhaps you should elaborate on your calculations; To me, 7.5 kJ doesn't look right.
 
gneill said:
Perhaps you should elaborate on your calculations; To me, 7.5 kJ doesn't look right.

M=F*r
F=m*α
α=ω/T
Ek=(Iω^2)/2
 
the_man said:
M=F*r
F=m*α
α=ω/T
Ek=(Iω^2)/2

I see a collection of formulas, at least one of which is rather dubious, but no calculations. Can you show your numerical work and explain what the steps are that your taking?
 

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