Why Does Torque Equal Force for a Torsion Dynamometer?

In summary, a torsion dynamometer is able to measure small forces with little friction and without displacement by compensating the force through the torsion force of a metallic band. This allows for torque comparison, as the magnitude of torque is proportional to the force multiplied by the length of the lever arm. The lever arm length is assumed to be constant and known, making it possible to calculate force from torque or vice versa.
  • #1
quietrain
655
2
does anyone know why for a torsion dynamometer, even though it measures the force, it can still be used as a torque comparison?

FROM
http://www.phywe.com/461/apg/4/pid/853/Torsionskraftmesser-0,01-N-.htm

" 1 PURPOSE
The 0.01 N torsion dynamometer allows to measure small
forces with little friction and without displacement.
A force acting on lever arm 4 is compensated through the
torsion force of a metallic band (torque comparison)."thank you!
 
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  • #2
The magnitude of the torque is simply the force multiplied by the length of the lever arm (in meters) when the angle between the lever arm and direction the force is applied is 90 degrees. I'm not sure if you're caught up in some sort of terminology confusion, but this is the standard definition for magnitude of torque, when it is synonymous with "moment" as used in the US (for us Mech. Engrs.).
 
  • #3
S_Happens said:
The magnitude of the torque is simply the force multiplied by the length of the lever arm (in meters) when the angle between the lever arm and direction the force is applied is 90 degrees. I'm not sure if you're caught up in some sort of terminology confusion, but this is the standard definition for magnitude of torque, when it is synonymous with "moment" as used in the US (for us Mech. Engrs.).

yes, i know that , but the thing is for the torsion dynamometer, it measures the force! and somehow that force is proportional to the torque?

does it then mean the length of the lever arm is always a constant and so i can say the forced measured is proportional to the torque?
 
  • #4
OK.

Maybe you're getting hung up on the statement of "...measures the force." This statement is NOT important, and can be misleading. The OUTPUT of the instrument is an indication of what force is applied to the lever arm. This does not mean that it is directly measuring the force and not simply calculating it from the torque and length of the lever arm (and it doesn't matter which way it is done). Like I already stated, and what you said you already "know," there is a very simple relationship between torque and force when the length of the lever arm is known.

The answer to your last question is yes, and good job in recognizing that. Maybe you're not confident in making the assumption that the lever arm is know or must be known for this instrument. From the simple formula, you can see that to solve for one variable you must have the other two. In this case, it is safe to assume that the lever arm is known. Looking at the picture (and being unfamiliar with this piece of equipment), you can also safely assume that the lever arm is what is shown and will not change. If it was able to change, then there would have to be a way for the instrument to know that (a simple calibration).

You say "yes, i know that..." but maybe not as completely as you think. Do not take that as an insult, but a suggestion to think a little bit more about a simple formula. The answer is quite simply...

If you want to calculate force from torque, or vice versa, all you need to know is the length of the lever arm. (assuming the angle between the lever arm and force is 90, and using/calculating the magnitude of the torque).
 
  • #5
i see thank you!
 

FAQ: Why Does Torque Equal Force for a Torsion Dynamometer?

Why is torque equal to force for a torsion dynamometer?

The reason for this is because a torsion dynamometer is designed to measure the twisting force, or torque, applied to it. The device is calibrated in such a way that when a certain amount of force is applied, it will twist by a certain amount. This allows for an accurate measurement of torque equal to the applied force.

How does a torsion dynamometer measure torque?

A torsion dynamometer typically consists of a shaft or beam that is attached to a stationary point at one end and a moveable point at the other end. When a force is applied to the moveable point, it will cause the shaft to twist. This twisting motion is measured and converted into a torque reading.

Can torque be measured without a torsion dynamometer?

Yes, torque can be measured using other devices such as a torque wrench or a strain gauge. However, a torsion dynamometer is specifically designed for measuring torque and is often preferred due to its high accuracy and sensitivity.

What are some common applications of torsion dynamometers?

Torsion dynamometers are commonly used in various industries for measuring torque in engines, motors, and other rotating machinery. They are also used in research and development to test the torque of new products or materials.

Are torsion dynamometers suitable for both high and low torque measurements?

Yes, torsion dynamometers can be designed to measure a wide range of torque values, from very low to very high. The sensitivity and accuracy of the device can be adjusted according to the specific needs of the application.

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