# Torque intersection problem

## Homework Statement

what is the torque if you know the the line of force intersects the center of the rotation ?

## The Attempt at a Solution

I think the torque will be T= ( f*sin (45) )*d
But I'm not sure will there be a torque or not ...the intersection of virtual line of force with the center of rotation is confusing me !

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Doc Al
Mentor
About what point are you trying to find the torque?

about the center of the rod

Doc Al
Mentor
about the center of the rod
In that case, what would the distance be in your formula for torque?

Torque is the ability of a force to rotate an object around a point.
T = F*r
The distance r is the perpendicular distance between the pivot point and the line of the force that works in on the point (virtual line).

So what is the perpendicular distance between the virtual line of force and the pivot point?

What now ??

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Doc Al
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What now ??
Where is the force being applied? I assume that the point indicated, which is apart from the center. (1 m to the left and 1 m up from the center.)

The easy way is to just extend the line of the force and see that it intersects the axis of rotation. That should immediately tell you what the torque is, without the need for any calculation.

But if you want to calculate torques from each component separately, that's fine also. You'll get the same answer.

Doc Al
Mentor
One thing to realize when calculating the torque using F*r*sinθ, is that θ is the angle between the force vector ($\vec{F}$) and the position vector ($\vec{r}$).

So you mean that the torque is gonna be zero, right !

right............

T= ( f*sin (0) )*r

okay ... one more question to be fully understood the topic ...assume that this left stick is under a pressure (the whole stick) ... Now How can I calculate the torque

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