2. Work  Work is done when a force moves an object over a distance  Work = force X distance or W = f X d  When a force is applied to an object, the force may or may not cause the object to move. If the force does not produce motion, NO WORK IS DONE! A force results in work ONLY if motion is produced.

3. Machines AA device that transfers mechanical energy from one object to another MMake work easier to perform by: 11) multiplying force 22) changing the direction or the distance over which a force is applied EEx: a wrench multiplies applied force when moving a tight bolt. EEx: a loading ramp attached to the back of the truck reduces the force but increases the distance the object must be moved.

4. Resistance and Effort  Resistance = the force a machine has to overcome  Effort = the force applied  Using a machine CAN reduce the amount of effort needed to overcome a given amount of resistance but a machine does NOT decrease the amount of work

5. Work  Ex: Suppose you lift a box weighing 450 Newtons up onto a 2 meter high platform. To light the box straight up by yourself, you would need to apply 450 Newtons of force over a distance of 2 meters.  W= f x d = 450 N x 2 m = 900 J

6. Work  HOWEVER, if you set up a rope and pulley system to change the direction and distance of the force required, you might have to pull in 9 meters of rope only using 100 Newtons of force:  W= f x d = 100 N x 9m = 900 J  So the TOTAL amount of work is the SAME using the pulley versus not using the pulley

7. 6 Simple Machines  Lever  Pulley  Wheel and axle  Inclined plane  Wedge  Screw

8. Lever  Consists of a rigid bar that can turn around a point called a fulcrum  Ex: pliers, crowbar

9. Pulley AA modified form of a lever. Can change direction of force or decrease the force needed to move a heavy object. EEx: clothes line

10. Wheel and axle  A modified form of a lever. Consists of a large wheel with a smaller wheel (or axle) in its center. They are connected so they turn together. Turning the outer wheel uses less force but must turn a greater distance.  Ex: bicycles, car steering wheels, doorknobs

11. Inclined plane  A flat surface with one end higher than the other.  Ex: wheelchair ramp, truck ramp

12. Wedge  Double-sided inclined plane. The effort force is applied by driving the wedge into something, like an ax into a log.  Ex: ax, knives, wood nails, chisels

13. Screw  An inclined plane wrapped around a wedge or cylinder  Ex: wood screws, bolts, car jacks

14. Complex Machines  Contains 2 or more simple machines  Ex: a bike has a wheel and axle, a pulley system and a lever.

15. Efficiency of machines  Machines are never 100% efficient  The amount of work done by any machines is ALWAYS less than the amount of work put into it  Some work is converted into heat energy and is wasted. Heat energy is produced because of rubbing together of the machine’s parts (friction).

16. Machine efficiency  A machine can be made more efficient by reducing friction.  Grease oil, and wax are good ways to reduce the friction between moving parts.  Sanding surfaces to make them smoother or using ball bearings between surfaces also reduces friction.