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| 183_notes:torque [2021/05/08 18:55] – [Torque] stumptyl | 183_notes:torque [2021/05/08 18:56] (current) – [Sign of the Torque comes from the Right-Hand Rule] stumptyl | ||
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| - | When working with forces and lever arms that exist is a plane (e.g., $x-y$ plane), the torque always points in the $z$-direction. So, it becomes useful to think about the torque as having a sign, either + or - depending on whether in points in the $+z$ or $-z$ direction. The " | + | When working with forces and lever arms that exist is a plane (e.g., $x-y$ plane),__// the torque always points in the $z$-direction//.__ So, it becomes useful to think about the torque as having a sign, either + or - depending on whether in points in the $+z$ or $-z$ direction. The " |
| To use this rule, point your fingers in the direction of the the lever arm (from the rotation point to the point of application of the of the force). Then, curl your fingers in the direction of the force. Your thumb will point in the direction of the torque. This works for any situation, but you might be confused about the sign. A simpler way of remembering it is using the picture on the right. This is somewhat analogous to having forces in different directions. | To use this rule, point your fingers in the direction of the the lever arm (from the rotation point to the point of application of the of the force). Then, curl your fingers in the direction of the force. Your thumb will point in the direction of the torque. This works for any situation, but you might be confused about the sign. A simpler way of remembering it is using the picture on the right. This is somewhat analogous to having forces in different directions. | ||
| - | The language often used to describe the torque direction is //into the page// and //out of the page//. It is the nature of cross products that the resultant is perpendicular to the plane defined by the vectors in the cross product. So, if the lever arm and the force vector appear on page (or screen), the torque will point into or out of the page (or screen). In the cases shown to the right, it means the vector associated with the torque points into the screen (negative, clockwise rotation) or out of the screen (positive, counter-clockwise rotation). | + | **The language often used to describe the torque direction is into the page and out of the page.** It is the nature of cross products that the resultant is perpendicular to the plane defined by the vectors in the cross product. So, if the lever arm and the force vector appear on page (or screen), the torque will point into or out of the page (or screen). In the cases shown to the right, it means the vector associated with the torque points into the screen (negative, clockwise rotation) or out of the screen (positive, counter-clockwise rotation). |
| ==== The Net Torque Causes Changes in Rotation ==== | ==== The Net Torque Causes Changes in Rotation ==== | ||