For an object in equilibrium the net torque acting on it vanishes only if each torque is
calculated about:
a common point?
To determine the torque acting on an object in equilibrium, we need to consider the point about which the torques are calculated. This point is called the axis of rotation or the pivot point.
For an object in equilibrium, the net torque acting on it must be zero. This means that the sum of all the torques acting on the object about any chosen axis of rotation must be zero.
To find the axis of rotation about which each torque is calculated, you can follow these steps:
1. Identify the object: Determine the object for which you want to calculate the torques.
2. Identify the forces: Identify all the forces acting on the object. These forces can be contact forces (e.g., applied forces, normal forces, friction forces) or non-contact forces (e.g., gravitational forces).
3. Determine the lever arm: For each force acting on the object, determine the perpendicular distance between the axis of rotation and the line of action of the force. This distance is called the lever arm.
4. Calculate the torque for each force: To calculate the torque for each force, multiply the magnitude of the force by the lever arm.
5. Choose the axis of rotation: Now, choose an axis of rotation. You can choose any point as the axis of rotation, but it is often helpful to choose a point where the torques from certain forces may cancel each other out.
6. Calculate the sum of the torques: Add up all the torques calculated in step 4. Take into account the direction of each torque, considering clockwise torques as positive and counterclockwise torques as negative.
7. Check if the net torque is zero: Determine if the sum of the torques calculated in step 6 is zero. If it is zero, then the object is in equilibrium with respect to the chosen axis of rotation.
Repeat steps 5-7 for different axis of rotation if needed, until you find an axis where the net torque is zero. This would be the axis about which each torque is calculated for an object in equilibrium.