1. Torque

2. Tough Nut • Which of the four arrangements is best for tightening a bolt? A B C D

3. Pivot Point • Rotation of a wheel or wrench takes place with an axis of rotation. • The point where the axis intersects the object is the pivot point. q q r pivot point

4. Lever Arm • The tangential force acts at a distance away from the pivot point. • The distance from the pivot to the force is called the lever arm, or moment arm. lever arm points out from the pivot r

5. Perpendicular Component • Only the perpendicular component of the force can affect the tangential acceleration. • For an angle (q) between the force (F) and lever arm (r), the perpendicular component is Fsinq. angle between lever arm and force q

6. Moment of Force • The force exerted on the lever arm is the moment of force. • This is called torque (t).

7. Changing a Tire • A wheel nut needs 95 N-m of torque. • A 45 cm wrench makes a 67° angle with the horizontal. • The horizontal force needed: 113° 67° r

8. Torque Wrench • Consider the product rFsinq. rF (0.7)2rF = (1.4)rF (0.87)rF (3r/2)(F/2) = (3/4)rF next