Torque

=Torque =

Torque results from the application of force to an object, which results in rotation around a fixed point. What torque actually does, is cause a change in the angular acceleration of an object. Take a hinged door, for example. If you push on the door, it creates torque, which causes the door to rotate about the hinge. There are several factors that determine the magnitude of torque, given in the equation below:

==== This equation can be analyzed by going back to the door example used previously. If you push the door harder, or farther away from the hinge, it opens faster. This is confirmed by the equation; a greater applied force, farther from the pivot point, produces greater torque. The final variable,"Ѳ", can also be explained with the example. Common sense says that pushing on the door perpendicular to its length will cause the greatest acceleration. Conversely, pushing parallel to the door will produce no torque, so the door will not rotate. These statements can be confirmed by simple trigonometry: sin90° = 1, and sin0° = 0. Any value between 90° and 0° will produce a torque of some lesser magnitude. ====

Torque in Equilibrium
For objects in equilibrium, the following rules can be applied:

 The net external torque must equal zero.
====These rules can be used to solve many problems, just by equating forces and torques on an object. To simplify the problem solving process, it is usually best to choose an axis that will make at least one torque zero. ====

Hand Rule
Torque is a vector that lies perpendicular to the plane of the position and force vectors. The direction can be determined by the right-hand rule:
 * 1) Point your fingers in the direction of the length (away from the pivot point).
 * 2) Rotate your hand until your palm points in the direction of the force.
 * 3) Your thumb now points in the direction of the torque.



Sample Problems
Two people are trying to get through the same door at the same time. If neither manages to move the door, what force is the person in red exerting? 

====<span style="font-family: 'Times New Roman',Times,serif; font-size: 110%;"> T<span style="font-family: 'Times New Roman',Times,serif; font-size: 80%;">red + T<span style="font-family: 'Times New Roman',Times,serif; font-size: 80%;">green = 0 ....................................... If the door is not moving, then the net torque must equal zero. ==== ====<span style="font-family: 'Times New Roman',Times,serif; font-size: 110%;"> T<span style="font-family: 'Times New Roman',Times,serif; font-size: 80%;">red = -T<span style="font-family: 'Times New Roman',Times,serif; font-size: 80%;">green ............................................ Separate the individual torques. ==== ====<span style="font-family: 'Times New Roman',Times,serif; font-size: 110%;">(rF)<span style="font-family: 'Times New Roman',Times,serif; font-size: 80%;">red = -(rF)<span style="font-family: 'Times New Roman',Times,serif; font-size: 80%;">green ..................................... Substitue using the equation (sinѲ = 1). ====