Torque when there is variable force

[fondbeech]

Homework Statement

There is a force that varies with the distance from the origin. Can I solve for the torque by integrating the force over the length of the object that the force acts on? Is it integral of F dr or F*r dr?

Homework Equations

torque=FxR

The Attempt at a Solution

I thought that torque could be the integral of F dr but I'm not sure if that is right.

 

[Redbelly98]

Welcome to Physics Forums.

Homework Statement

There is a force that varies with the distance from the origin. Can I solve for the torque by integrating the force over the length of the object that the force acts on? Is it integral of F dr or F*r dr?

Homework Equations

torque=FxR

The Attempt at a Solution

I thought that torque could be the integral of F dr but I'm not sure if that is right.

Instead of being given the force, you should really be given the force per unit length (units of N/m).

Calling f the force per unit length, the force on a small section of length dr would then be f·dr. So, what would be the torque on that section? From there, it should be evident how to get the total torque.