Calculate Intensity of Braking Moment - Rotational Movement Flywheel

In summary, the braking moment intensity is equal to the speed with which the angular moment changes.
  • #1
Faefnir
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A flywheel with a inertia moment of ##245 kg \cdot m^2## rotates making 20 round per second. The wheel stops 20 minutes after a braking moment action. Calculate the intensity of the braking moment

$$ \omega = 20 \frac{round}{s} = 126 \frac{rad}{s} $$
$$ t = 20 min = 1200 s $$

The braking moment intensity is equal to the speed with which the angular moment changes. Because the wheel is stopped at the time ## t = 1200 s##

$$ t = 1200 s $$
$$ \Delta L = I \cdot \omega $$
$$ \tau = \frac{I \cdot \omega}{t} = \frac{245 kg \cdot m^2 \cdot 126 \frac{rad}{s}}{1200 s} = 25.725 N \cdot m $$

The text provides a result of ## 513 N \cdot m ##. What was wrong with reasoning?

 
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  • #2
Your reasoning looks good to me. I suspect that the problem's given values have been altered at some point in order to make it a "new" question, but the answer was not updated to reflect the change.

Note that the given answer is almost exactly 20 times what you've calculated. If I were to guess I' d say that the original question had a deceleration time of 1 minute rather than 20 minutes.
 
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  • #3
It looks as if the book answer is a factor 20 off. Perhaps an earlier version of the exercise let it come to a stop in 1 minute ? And they forgot to update the answer in the back ?

PS don't give a 5 decimal answer if all you are given is one or two decimals in the problem statement.
 
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  • #4
I am stumped by your answer guide, as well. It's been awhile since I have solved one of these, so I went back and looked up to make sure I am figuring correctly, but I came up with the same answer that you did. In fact, I calculated that a 513Nm torque would stop it in 60 seconds.
 
  • #5
Warm feeling that three of us are on the same line of tought ... :rolleyes:
 
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Related to Calculate Intensity of Braking Moment - Rotational Movement Flywheel

What is the formula for calculating the intensity of braking moment in rotational movement of a flywheel?

The formula for calculating the intensity of braking moment in rotational movement of a flywheel is: I = MR², where I is the intensity of braking moment, M is the mass of the flywheel, and R is the radius of the flywheel.

What are the units of measurement for the intensity of braking moment?

The units of measurement for the intensity of braking moment are Newton-meters (Nm) or Kilogram-meters squared per second (kgm²/s²).

How does the intensity of braking moment affect the rotational movement of a flywheel?

The intensity of braking moment is directly proportional to the angular acceleration of the flywheel. This means that a higher intensity of braking moment will result in a greater decrease in the rotational speed of the flywheel.

What factors can affect the intensity of braking moment in a flywheel?

The intensity of braking moment in a flywheel can be affected by several factors, including the mass and radius of the flywheel, the coefficient of friction between the flywheel and braking mechanism, and the force applied to the braking mechanism.

Is there a maximum intensity of braking moment that can be applied to a flywheel?

Yes, there is a maximum intensity of braking moment that can be applied to a flywheel. This is known as the yielding moment, which is the point at which the flywheel will begin to deform or break under the applied braking force.

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