1. Chapter 11 Section 4 Simple Machines

2. What is a Simple Machine?  Is a machine that takes one force and changes its direction, distance, or strength.  A simple machine has few or no moving parts.  Simple machines make work easier. Introduction

3. Simple Machines  Effort – force you apply to a machine  Output- the force a machine supplies  Load- the object moved  Simple machines can increase the force we apply.

4. Simple Machines  Work = force x distance  Simple machines make work easier because it can increase force needed to move objects or they can decrease the amount of force needed to move the object.  Examples of simple machines are levers, pulleys, wedges, wheel & axle, inclined planes, and screws.

5. What are Levers ?  A lever is a bar that rests on a support called a fulcrum which lifts or moves loads.  Fulcrum- the pivot point for a lever  Levers multiply effort, distance, and speed.

6. Levers-First Class  In a first class lever the fulcrum is in the middle and the load and effort is on either side.  The effort and out move in opposite directions.  Think of a see-saw

7. Levers-Second Class  In a second class lever the fulcrum is at the end, with the load and effort on one side.  Think of a wheelbarrow Effort ^

8. Levers-Third Class  In a third class lever the fulcrum is again at the end, but the effort is in the middle  Think of a pair of chop sticks

9. Wheels and Axles  The wheel and axle are a simple machine.  The axle is a rod that goes through the wheel which allows the wheel to turn to lift or move loads.  Gears are a form of wheels and axles

10. Pulleys  Pulleys are wheels and axles with a groove around the outside used to raise or lower a load.  A pulley needs a rope, chain or belt around the groove to make it do work.

11. Inclined Planes  An inclined plane is a slanting surface connecting a lower level to a higher level.  Inclined planes make the work of moving things easier.

12. Wedges  Two inclined planes joined back to back.  Wedges are used to split things.  Wedges are also used to lift objects.

13. Screws  A screw is an inclined plane wrapped around a pole which holds things together or lifts materials.  The inclined plane allows the screw to move itself when rotated.

14. Compound Machines  Compound machines- two or more simple machines used to move a load.  A compound machine can also use the same simple machine multiple times.  Efficiency- ratio of input energy to output work.

15. Compound Machine  Bulldozer – lever and wedge  Wheelbarrow- levers, wheel and axle,  Scissors- levers and wedges  Hand drill- screw and wheel and axle  Elevator- multiple pulleys