Why does “torque” have 2 different units?
On various websites I see torque expressed as kgm but I was always taught torque is Nm or kgm^2/s^2. These are clearly not the same, so why are they called the same and when do I use one or the other?
angular-momentum torque units
asked 3 hours ago
sparposparpo
83
add a comment |
On various websites I see torque expressed as kgm but I was always taught torque is Nm or kgm^2/s^2. These are clearly not the same, so why are they called the same and when do I use one or the other?
angular-momentum torque units
asked 3 hours ago
sparposparpo
83
1
Don’t trust websites for introductory physics help. There’s a lot of crap and noise out there. The one you were always taught is perfectly right!
– knzhou
3 hours ago
@knzhou I see this unit of torque kg/m , in the details of electric motors. They always give the torque of an electric motor in kg/m. Do they just call it "torque" but mean something else?
– sparpo
3 hours ago
@knzhou Actually "kg/m" was probably just a mistake on this website, they probably meant kg*m.
– sparpo
3 hours ago
It has any number of units, since there are any number of unit systems. In cgs it has unit $dyne cdot cm$. If you stick to a single unit system you cannot go wrong. My advise is mksi, so $Nm$.
– my2cts
2 hours ago
@sparpo, kg is a unit of mass, and N is a unit of force. kg-m is NOT a unit of torque. This usage no doubt comes from the usage of ft-lb in the English system, but what most people don't realize is that there are pounds-force and pounds-mass, and the two units differ by a factor of 32.2.
– David White
2 hours ago
add a comment |
On various websites I see torque expressed as kgm but I was always taught torque is Nm or kgm^2/s^2. These are clearly not the same, so why are they called the same and when do I use one or the other?
angular-momentum torque units
asked 3 hours ago
sparposparpo
83
On various websites I see torque expressed as kgm but I was always taught torque is Nm or kgm^2/s^2. These are clearly not the same, so why are they called the same and when do I use one or the other?
angular-momentum torque units
angular-momentum torque units
asked 3 hours ago
sparposparpo
83
asked 3 hours ago
sparposparpo
83
edited 3 hours ago
sparpo
asked 3 hours ago
sparposparpo
83
asked 3 hours ago
sparposparpo
83
asked 3 hours ago
sparposparpo
83
83
1
Don’t trust websites for introductory physics help. There’s a lot of crap and noise out there. The one you were always taught is perfectly right!
– knzhou
3 hours ago
@knzhou I see this unit of torque kg/m , in the details of electric motors. They always give the torque of an electric motor in kg/m. Do they just call it "torque" but mean something else?
– sparpo
3 hours ago
@knzhou Actually "kg/m" was probably just a mistake on this website, they probably meant kg*m.
– sparpo
3 hours ago
It has any number of units, since there are any number of unit systems. In cgs it has unit $dyne cdot cm$. If you stick to a single unit system you cannot go wrong. My advise is mksi, so $Nm$.
– my2cts
2 hours ago
@sparpo, kg is a unit of mass, and N is a unit of force. kg-m is NOT a unit of torque. This usage no doubt comes from the usage of ft-lb in the English system, but what most people don't realize is that there are pounds-force and pounds-mass, and the two units differ by a factor of 32.2.
– David White
2 hours ago
add a comment |
1
Don’t trust websites for introductory physics help. There’s a lot of crap and noise out there. The one you were always taught is perfectly right!
– knzhou
3 hours ago
@knzhou I see this unit of torque kg/m , in the details of electric motors. They always give the torque of an electric motor in kg/m. Do they just call it "torque" but mean something else?
– sparpo
3 hours ago
@knzhou Actually "kg/m" was probably just a mistake on this website, they probably meant kg*m.
– sparpo
3 hours ago
It has any number of units, since there are any number of unit systems. In cgs it has unit $dyne cdot cm$. If you stick to a single unit system you cannot go wrong. My advise is mksi, so $Nm$.
– my2cts
2 hours ago
@sparpo, kg is a unit of mass, and N is a unit of force. kg-m is NOT a unit of torque. This usage no doubt comes from the usage of ft-lb in the English system, but what most people don't realize is that there are pounds-force and pounds-mass, and the two units differ by a factor of 32.2.
– David White
2 hours ago
1
1
Don’t trust websites for introductory physics help. There’s a lot of crap and noise out there. The one you were always taught is perfectly right!
– knzhou
3 hours ago
Don’t trust websites for introductory physics help. There’s a lot of crap and noise out there. The one you were always taught is perfectly right!
– knzhou
3 hours ago
@knzhou I see this unit of torque kg/m , in the details of electric motors. They always give the torque of an electric motor in kg/m. Do they just call it "torque" but mean something else?
– sparpo
3 hours ago
@knzhou I see this unit of torque kg/m , in the details of electric motors. They always give the torque of an electric motor in kg/m. Do they just call it "torque" but mean something else?
– sparpo
3 hours ago
@knzhou Actually "kg/m" was probably just a mistake on this website, they probably meant kg*m.
– sparpo
3 hours ago
@knzhou Actually "kg/m" was probably just a mistake on this website, they probably meant kg*m.
– sparpo
3 hours ago
It has any number of units, since there are any number of unit systems. In cgs it has unit $dyne cdot cm$. If you stick to a single unit system you cannot go wrong. My advise is mksi, so $Nm$.
– my2cts
2 hours ago
It has any number of units, since there are any number of unit systems. In cgs it has unit $dyne cdot cm$. If you stick to a single unit system you cannot go wrong. My advise is mksi, so $Nm$.
– my2cts
2 hours ago
@sparpo, kg is a unit of mass, and N is a unit of force. kg-m is NOT a unit of torque. This usage no doubt comes from the usage of ft-lb in the English system, but what most people don't realize is that there are pounds-force and pounds-mass, and the two units differ by a factor of 32.2.
– David White
2 hours ago
@sparpo, kg is a unit of mass, and N is a unit of force. kg-m is NOT a unit of torque. This usage no doubt comes from the usage of ft-lb in the English system, but what most people don't realize is that there are pounds-force and pounds-mass, and the two units differ by a factor of 32.2.
– David White
2 hours ago
add a comment |
2 Answers
2
active
oldest
votes
Those other sources were probably referring to kilogram-force instead of Newtons. Given the constant conversion between mass and weight on Earth (i.e., $g = 9.8,textrm{m/s^2}$), mass and weight units are often used interchangeably in non-scientific contexts. So, torque can be expressed in kgf-m, where 1 kgf is the weight of 1 kg on Earth's surface. Notice that this is a multiplication, not a division. Units of kgf/m would be completely incorrect.
answered 3 hours ago
Mark HMark H
12.1k22340
add a comment |
The non SI unit is often written as 1 kg-m and is equal to 9.8 N m.
In such a case the 1 kg refers to the unit 1 kg force which is the weight of one kilogram.
Another unit is the Imperial (and US) unit the pound-foot which is equal to approximately 1.36 N m.
Here the unit of force is the pound force.
answered 3 hours ago
FarcherFarcher
47.8k33796
add a comment |
Your Answer
StackExchange.ifUsing("editor", function () {
return StackExchange.using("mathjaxEditing", function () {
StackExchange.MarkdownEditor.creationCallbacks.add(function (editor, postfix) {
StackExchange.mathjaxEditing.prepareWmdForMathJax(editor, postfix, [["$", "$"], ["\\(","\\)"]]);
});
});
}, "mathjax-editing");
StackExchange.ready(function() {
var channelOptions = {
tags: "".split(" "),
id: "151"
};
initTagRenderer("".split(" "), "".split(" "), channelOptions);
StackExchange.using("externalEditor", function() {
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled) {
StackExchange.using("snippets", function() {
createEditor();
});
}
else {
createEditor();
}
});
function createEditor() {
StackExchange.prepareEditor({
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: false,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: null,
bindNavPrevention: true,
postfix: "",
imageUploader: {
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
},
noCode: true, onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
});
}
});
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fphysics.stackexchange.com%2fquestions%2f453425%2fwhy-does-torque-have-2-different-units%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
Those other sources were probably referring to kilogram-force instead of Newtons. Given the constant conversion between mass and weight on Earth (i.e., $g = 9.8,textrm{m/s^2}$), mass and weight units are often used interchangeably in non-scientific contexts. So, torque can be expressed in kgf-m, where 1 kgf is the weight of 1 kg on Earth's surface. Notice that this is a multiplication, not a division. Units of kgf/m would be completely incorrect.
answered 3 hours ago
Mark HMark H
12.1k22340
add a comment |
Those other sources were probably referring to kilogram-force instead of Newtons. Given the constant conversion between mass and weight on Earth (i.e., $g = 9.8,textrm{m/s^2}$), mass and weight units are often used interchangeably in non-scientific contexts. So, torque can be expressed in kgf-m, where 1 kgf is the weight of 1 kg on Earth's surface. Notice that this is a multiplication, not a division. Units of kgf/m would be completely incorrect.
answered 3 hours ago
Mark HMark H
12.1k22340
add a comment |
Those other sources were probably referring to kilogram-force instead of Newtons. Given the constant conversion between mass and weight on Earth (i.e., $g = 9.8,textrm{m/s^2}$), mass and weight units are often used interchangeably in non-scientific contexts. So, torque can be expressed in kgf-m, where 1 kgf is the weight of 1 kg on Earth's surface. Notice that this is a multiplication, not a division. Units of kgf/m would be completely incorrect.
answered 3 hours ago
Mark HMark H
12.1k22340
Those other sources were probably referring to kilogram-force instead of Newtons. Given the constant conversion between mass and weight on Earth (i.e., $g = 9.8,textrm{m/s^2}$), mass and weight units are often used interchangeably in non-scientific contexts. So, torque can be expressed in kgf-m, where 1 kgf is the weight of 1 kg on Earth's surface. Notice that this is a multiplication, not a division. Units of kgf/m would be completely incorrect.
answered 3 hours ago
Mark HMark H
12.1k22340
answered 3 hours ago
Mark HMark H
12.1k22340
answered 3 hours ago
Mark HMark H
12.1k22340
answered 3 hours ago
Mark HMark H
12.1k22340
12.1k22340
add a comment |
add a comment |
The non SI unit is often written as 1 kg-m and is equal to 9.8 N m.
In such a case the 1 kg refers to the unit 1 kg force which is the weight of one kilogram.
Another unit is the Imperial (and US) unit the pound-foot which is equal to approximately 1.36 N m.
Here the unit of force is the pound force.
answered 3 hours ago
FarcherFarcher
47.8k33796
add a comment |
The non SI unit is often written as 1 kg-m and is equal to 9.8 N m.
In such a case the 1 kg refers to the unit 1 kg force which is the weight of one kilogram.
Another unit is the Imperial (and US) unit the pound-foot which is equal to approximately 1.36 N m.
Here the unit of force is the pound force.
answered 3 hours ago
FarcherFarcher
47.8k33796
add a comment |
The non SI unit is often written as 1 kg-m and is equal to 9.8 N m.
In such a case the 1 kg refers to the unit 1 kg force which is the weight of one kilogram.
Another unit is the Imperial (and US) unit the pound-foot which is equal to approximately 1.36 N m.
Here the unit of force is the pound force.
answered 3 hours ago
FarcherFarcher
47.8k33796
The non SI unit is often written as 1 kg-m and is equal to 9.8 N m.
In such a case the 1 kg refers to the unit 1 kg force which is the weight of one kilogram.
Another unit is the Imperial (and US) unit the pound-foot which is equal to approximately 1.36 N m.
Here the unit of force is the pound force.
answered 3 hours ago
FarcherFarcher
47.8k33796
answered 3 hours ago
FarcherFarcher
47.8k33796
answered 3 hours ago
FarcherFarcher
47.8k33796
answered 3 hours ago
FarcherFarcher
47.8k33796
47.8k33796
add a comment |
add a comment |
Thanks for contributing an answer to Physics Stack Exchange!
- Please be sure to answer the question. Provide details and share your research!
But avoid …
- Asking for help, clarification, or responding to other answers.
- Making statements based on opinion; back them up with references or personal experience.
Use MathJax to format equations. MathJax reference.
To learn more, see our tips on writing great answers.
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fphysics.stackexchange.com%2fquestions%2f453425%2fwhy-does-torque-have-2-different-units%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
1
Don’t trust websites for introductory physics help. There’s a lot of crap and noise out there. The one you were always taught is perfectly right!
– knzhou
3 hours ago
@knzhou I see this unit of torque kg/m , in the details of electric motors. They always give the torque of an electric motor in kg/m. Do they just call it "torque" but mean something else?
– sparpo
3 hours ago
@knzhou Actually "kg/m" was probably just a mistake on this website, they probably meant kg*m.
– sparpo
3 hours ago
It has any number of units, since there are any number of unit systems. In cgs it has unit $dyne cdot cm$. If you stick to a single unit system you cannot go wrong. My advise is mksi, so $Nm$.
– my2cts
2 hours ago
@sparpo, kg is a unit of mass, and N is a unit of force. kg-m is NOT a unit of torque. This usage no doubt comes from the usage of ft-lb in the English system, but what most people don't realize is that there are pounds-force and pounds-mass, and the two units differ by a factor of 32.2.
– David White
2 hours ago