Catalyst

1. Catalyst If you missed the torque notes, please pick up a Week 16 lesson sheet by the door and get your notes from someone. • What is the equation for torque? • What is the torque on an object that has a 20 N force applied with a lever arm that is 1.5 m long at an angle of 65.0°? • What is the torque on an object that has a 10 N force applied at a perpendicular angle if the lever arm is 2.5 m?

2. Today’s Agenda

3. Outside the Center of Mass What happens when you apply a force somewhere other than the center of mass?

4. Outside the Center of Mass • What happens when you apply a force somewhere other than the center of mass? • The object will ROTATE! • The force that causes rotational motion around some point (the center of mass or some other fixed point), is called TORQUE

5. Torque Review Torque is the force that causes rotational motion around some point (usually the center of mass) It depends on the force applied (F), length of the lever arm(d) and the anglebetween the force and lever arm. The more perpendicularthe angle, the more torque. Torque can either be positive (counter-clockwise) or negative (clockwise) based on what way it causes the object to rotate

6. Units: N•m The quantity “dsin ”is the perpendicular distance from the axis to the direction of the force. Torque

7. Balancing Torques • When you don’t want an object to rotate and you have two forces applied on either side of the center of mass, you need to balance their torques! • Best Example: See-Saw  • HOW TO DO IT: • 1. Take Torque 1 and make it equal to Torque 2 (assume perpendicular angles) • A. τ1 = τ2 • B. F1d1sin90 = F2d2sin90 • C. F1d1 = F2d2 • Solve for what you don’t know!

8. See Saw Example • Two kids are on a see saw. If kid A weighs 300 N and is 5 m from the center, and kid B weighs 450 N, where should kid B sit so that they are perfectly balanced? • Note: Their weight is the force! • F1d1 = F2d2 • (300)(5) = (450)(d2) • d2 = 3.33 m

9. Guided Practice Two kids are on a 12 m see saw. If kid A weighs 400 N and is 5.5 m from the center, and kid B weighs 600 N, where should kid B sit so that they are perfectly balanced?

10. Guided Practice • You have two wrenches, one being 0.1 m in length, and the other being 0.25 meters in length. How much torque would you get if you applied 400 N of force to the 0.25 m length wrench? How much force would you need to apply to the 0.1 m length wrench to get the same amount of torque? • Even though this isn’t a see-saw, this is still a problem where you need to balance torques!

11. Today’s Agenda

12. Warm Up Problem A wrench is 0.20 m long. If you apply 400 N of force at a perpendicular angle, how much torque is used to rotate the bolt?

13. Guided Practice • A steering wheel has a diameter of 0.28 m. If you apply 300 N of force when turning it (with one hand), how much torque results? • Assume the angle is perpendicular!

14. Guided Practice Two kids are on a 10 m see saw. If kid A weighs 500 N and is 4.5 m from the center, and kid B weighs 600 N, where should kid B sit so that they are perfectly balanced?

15. Guided Practice • You have two wrenches, one being 0.2 m in length, and the other being 0.3 meters in length. How much torque would you get if you applied 200 N of force to the 0.3 m length wrench? How much force would you need to apply to the .2 m length wrench to get the same amount of torque? • Even though this isn’t a see-saw, this is still a problem where you need to balance torques!

16. Today’s Agenda

17. Exit Slip • 1. Torque causes an object to ________. • a. Fly • b. Rotate • c. Speed up • d. Move in a straight line • 2. What angle provides the greatest torque? • 3. We apply a perpendicular force of 10 N to an object 6 m from its center of mass. What is the torque being applied? • 4. True or false: A longer lever arm provides more torque. • 5. What is the equation for torque?