1. Static Equilibrium Physics Chapter 11.3

2. Objectives Define Torque Analyze Forces acting on an object Identify requirements for Static Equilibrium Show understanding –Conceptual Problems –Quantitative Problems

3. What is Torque - Torque = Force x Distance Units: Newtons x Meters (N-m) Torque causes rotation –Torque > 0 counter-clockwise rotation (CCW) –Torque < 0 clockwise rotation (CW)

4. See-Saw Example Heavy person on the left –CCW Torque Heavy person on the right –CW Torque

5. Conceptual Questions Two forces produce the same torque, does it follow that they have the same magnitude? Explain. No. Torque depends both upon magnitude of the force and distance from the axis of rotation (called moment arm). A small force can produce the same torque as a large force if applied farther from the axis of rotation

6. CQ2 Sometimes, even with a wrench, one cannot loosen a nut that is frozen tightly to a bolt. One trick is to slip a long pipe over the wrench handle, thus extending the length of the handle. Explain why this works. The applied force acts at a greater distance thereby increasing the torque.

7. What does Static Equilibrium mean? Basically it means that the object isn’t moving –Net force in the x-direction = 0 –Net force in the y-direction = 0 –Net torque = 0 CCW Torque = CW Torque

8. Flow Chart 1.Is there a natural point of rotation? If no, go to 2. If yes, go to 3. 2.Pick a point which has an unknown force acting on it and use it as the point of rotation. 3.Measure all distances to forces from this point. 4.Determine whether each force would produce a CW or CCW torque. 5.Set all CW torques equal to all CCW torques. 6.Solve algebraically – remember each torque is a force acting at a distance.

9. Web References www.edinformatics.com/il/il_physics.htm www.fearofphysics.com/index.html www.walter-fendt.de/ph14e/

10. Group Work Visit assigned website and develop problem for the rest of class to solve. Be ready to discuss pros and cons of your assigned site.

11. Objectives Define Torque Analyze Forces acting on an object Identify requirements for Static Equilibrium Show understanding –Conceptual Problems –Quantitative Problems

12. THANKS Comments/Critique