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Describe how the magnitude of a torque depends on the magnitude of the lever arm and the angle the force vector makes with the lever arm; Determine the sign (positive or negative) of a torque using the right-hand rule; Calculate individual torques about a common axis and sum them to find the net torque
NOTE: here the lever arm = (force position - axis position). If signs are carefully kept, the sign of the force times the lever arm sign will successfully give the sign of the resulting torque.
What is torque? Crudely speaking, torque is "twisting or turning ability" of a force that can: change the angular velocity of an object (i.e. speed up or slow down rotation) cause a twisting or bending distortion of an object. A force with a "line of action" that does not cross the axis of rotation results in torque. Note:
The ability of a force to rotate an object about an axis is called torque. Experiments indicate that the rod in the figure is balanced if r1 F1 = r2 F2. This suggests that torque = r⊥ F, where r⊥ (referred to as lever arm) is the perpendicular distance from the location of force to the pivot.
A positive torque is one that causes an object in the x-yplane to rotate in the counter-clockwise direction, while negative torques are those the cause an object to rotate in the clockwise direction.
Find the lever arm (or moment arm) by extending the line of the force and drawing a line from the axis of rotation so that is crosses the line of the force at a right angle. Finding the lever arm
LEVER ARM: The lever arm is the perpendicular distance from the axis of rotation to the line of action. Finding the lever arm is usually one of the hardest parts of torque problems. Start by finding ‘r’, which is the distance from the axis of rotation to the point where the force is applied.
