# Torque: Applied Forces Pos/Neg?

• DameLight
In summary, when finding the direction of the torque, you must use the right hand rule for each individual torque before finding the net torque.
DameLight
Hi,

I have a question regarding the forces applied on an object that create the torque. I understand that the resulting torque is pos if the object turns counter clock wise and is neg if it turns clock wise and that you can also use the right hand rule to find the direction of the net torque.

I found the right answer for my homework by making some of the resulting torques negative, but I don't understand why they are negative.

Particularly one such problem where there is a circle. One of the forces is tangent and pointing up toward the E most point of the circle. The answer needs this to be neg, but the right hand rule makes it pos?

Was I suppose to be looking for the difference in the resulting torques? But that doesn't make any sense since the net torque is the sum of the torques found.

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Never assign a negative value to a force when determining the direction of the torque. Use right hand rule, clockwise is plus and counterclockwise is negative, or the other way around if you wish.

Conclusion:

When finding the torque, the magnitude is found through the equation
but to find the direction you must use the right hand rule for each individual torque before finding the net torque. The ones in opposite directions will cancel each other out and then you will use the right hand rule again to find the direction of the net torque.

The key is that you must assign opposite signs to torques on ccw and cw motion. It doesn't matter which sign you use although the convention is that ccw is positive and cw is negative.

Ellispson
Sorry if this is obvious but... It's important not to just memorise that equation but to understand that it comes from the geometry of the situation. What I mean is when presented with a drawing that already has some random angle marked θ do check it's the correct angle to use in the calculation.

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CWatters said:
Sorry if this is obvious but...

Yes, I understand that the angle you need has to be correct in reference with your chosen coordinate system.

## 1. What is torque?

Torque is a measure of the rotational force applied to an object. It is a vector quantity, meaning it has both magnitude and direction.

## 2. How is torque calculated?

Torque is calculated by multiplying the magnitude of the force applied to an object by the distance from the axis of rotation to the point where the force is applied. The formula for torque is T = F x d, where T is torque, F is the force, and d is the distance.

## 3. What is the difference between positive and negative torque?

Positive torque is when the force applied causes an object to rotate in a counterclockwise direction, while negative torque is when the force applied causes an object to rotate in a clockwise direction. This is determined by the direction of the force in relation to the axis of rotation.

## 4. How is torque related to rotational equilibrium?

For an object to be in rotational equilibrium, the net torque acting on it must be zero. This means that the clockwise and counterclockwise torques must be equal and cancel each other out. Torque is therefore essential in understanding and predicting the motion of objects in rotational equilibrium.

## 5. What are some real-life applications of torque?

Torque is used in many everyday objects and activities, such as opening a door, using a wrench, and riding a bicycle. It is also important in more complex systems, such as engines, turbines, and industrial machinery. Understanding torque is crucial in designing and maintaining these systems to ensure proper functioning and safety.

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