Torque and equilibrium; concept problem

In summary, when considering equilibrium, it is important to include both net force and net torque. The force from torque is considered in the net force acting on the body, as it can contribute to creating a net torque even if it does not directly contribute to the net force. Both net force and net torque need to be taken into account for a body to be in equilibrium.
  • #1
alpha372
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Homework Statement



I'm just trying to understand why the force from net torque isn't included in net force when considering equilibrium: Why isn't the force from torque part of the net forces acting on a body?

Homework Equations


if net force = 0 and net torque = 0 then the body is in equilibrium;
net force = ma, torque = Frsin@, where @ is theta


The Attempt at a Solution


It seems like the force required for torque should be part of the net forces acting on the body.
 
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  • #2
"Net force" is not a force, it's the sum of individual forces. You can certainly have forces acting on something so as to create a net torque, yet those same forces add up to zero net force. For example: a vertical force to the right of center and an equal but opposite vertical force to the left of center.

And you can also have a net force on a body with zero net torque.
 
  • #3
Doc Al said:
"Net force" is not a force, it's the sum of individual forces.

Agreed.

Your example helped me:
You can certainly have forces acting on something so as to create a net torque, yet those same forces add up to zero net force. For example: a vertical force to the right of center and an equal but opposite vertical force to the left of center.

Thanks.

So from this I now believe that the force from the torque actually is considered in the net force acting on the object. Now I am starting to understand why both net force and net torque need to be included for equilibrium.
 
Last edited:

1. What is torque and how is it related to equilibrium?

Torque is a measure of the force that causes an object to rotate around an axis. It is related to equilibrium because when the net torque acting on an object is zero, the object is in rotational equilibrium, meaning it is not rotating.

2. How is torque calculated?

Torque is calculated by multiplying the force applied to an object by the distance from the axis of rotation to the point where the force is applied. Mathematically, it is represented as torque = force x distance.

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

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

4. How does the lever arm affect torque?

The lever arm is the distance between the axis of rotation and the point where the force is applied. A longer lever arm will result in a greater torque, while a shorter lever arm will result in a smaller torque.

5. Can an object be in equilibrium if it is experiencing a torque?

Yes, an object can be in equilibrium even if it is experiencing a torque. This is because there can be opposing torques acting on the object, resulting in a net torque of zero and the object remaining in rotational equilibrium.

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