# What is significance of torque

1. Feb 9, 2012

### Arslan

or you can say what is the physical interpertation of torque. i know the mathemetics of it but whats its significance in practical terms.

2. Feb 9, 2012

### DaveC426913

What? You mean you want to know how it applies to the real world?

Like how you use a wrench to tighten a nut on a bolt? Or rev an engine to accelerate your car?

3. Feb 9, 2012

### Dr Lots-o'watts

Using a screwdriver is a rather good way to feel what torque is.

4. Feb 11, 2012

### Arslan

let me put my question this way
why torque is defined as F*r why not F*r^2

5. Feb 11, 2012

### tiny-tim

Hi Arslan!

Torque is turny-force, and moment of inertia is turny-mass.

Mass is the ratio of linear force to linear acceleration …

twice the force gives twice the acceleration.​

Moment of inertia is the ratio of torque (angular force) to angular acceleration …

twice the torque gives twice the angular acceleration.

6. Feb 11, 2012

### sophiecentaur

Reasonable question.
The pragmatic answer is that your suggested alternative won't give you the right answer when you try to calculate what will balance what. Torque is a quantity, like Force that can be used to model and understand mechanical situations AND to predict what will happen. The proof of the pudding is in the eating.

The more rigorous answer is that angular momentum is a very basic quantity in the Universe - just as linear momentum is. The formulae for linear motion, such as
Force = mass times acceleration
momentum = mass times velocity
and others, are well known. (?)

There are equivalents in the 'rotational world' and Torque turns up in those formulae, along with Moment of Inertia and Angular Momentum etc.
You would need to read further if you want more details and some of those formulae.

7. Feb 11, 2012

### Neandethal00

I think of torque as a force that causes rotational motion.

F = ma; here force F causes linear motion, with linear acceleration a.

Torque τ = Iα ; α is angular acceleration and moment of inertia I is related to mass.

Similarity between this 2 equations seem to be what is linear (motion in straight line) and angular (motion in circle).

8. Feb 11, 2012

### Nehmo

What would be the advantage of defining torque as F*r^2?