Final answer:
Net torque is the sum of individual torques taking into account their magnitude, direction, and distance from the axis of rotation. It is calculated using the formula τ = r × F and is influenced by factors like friction that can generate opposing torques.
Step-by-step explanation:
The concept being asked about is torque, which is a measure of the force causing an object to rotate about an axis. To calculate the net torque, one must consider both the magnitude of each force applied and its distance from the axis of rotation, known as the lever arm. The direction of the net torque depends on whether the individual torques are causing clockwise or counterclockwise rotation.
To calculate the net torque about an axis through O perpendicular to the page, one would use the formula τ = r × F, where r is the perpendicular distance from the axis to the line of action of the force, and F is the magnitude of the force. For example, the torque of a 40-N force with a lever arm length of 0.5 meters around the axis through O would be 20 N · m (assuming the lever arm is perpendicular to the force vector). Direction is given by the right-hand rule or by determining the sense of rotation (clockwise is typically considered negative, counterclockwise is positive).
If there are opposing forces, such as friction, their torques should also be taken into account. Angular acceleration (α) can then be found using the equation α = Στ/I, where I is the moment of inertia. If a frictional force is present, it will contribute a negative torque that must be subtracted from the sum of other torques to find the net torque.