Objectives

1. Section 2 Simple Machines Chapter 12 Objectives • Nameand describe the six types of simple machines. • Discussthe mechanical advantage of different types of simple machines. • Recognize simple machines within compound machines.

2. Section 2 Simple Machines Chapter 12 Bellringer You may not think of a door as a simple machine, but it is one. It functions like a lever. Like other levers, when you exert a force on it (an input force), a force is exerted along the entire door (the output force).

3. Section 2 Simple Machines Chapter 12 Bellringer, continued 1. For all levers, one point along the lever stays still while the rest of the lever moves. This point is called the fulcrum. Where is the fulcrum of a door? 2. You can push at any point along the width of a door and it will open. Which position requires the least force: pushing the door near the hinges, in the middle, or near the side farthest from the hinges? (Hint: Which of these feels easiest to do?) 3. If you are trying to prop the door open, but your only doorstop is not very heavy, is it likely to work best near the hinges, in the middle, or near the side farthest from the hinges?

4. Section 2 Simple Machines Chapter 12 The Lever Family • The most basic machines are calledsimple machines. • The six types of simple machines are divided into two families.

5. Section 2 Simple Machines Chapter 12 The Lever Family, continued • Levers have a rigid arm and a fulcrum. • Levers are divided into three classes. • All first-class levers have a fulcrum located between the points of application of the input and output forces. • In a second-class lever, the fulcrum is at one end of the arm and the input force is applied to the other end. • Third-class levers multiply distance rather than force. As a result, they have a mechanical advantage of less than 1.

6. Section 2 Simple Machines Chapter 12 Levers

7. Section 2 Simple Machines Chapter 12 Lever

8. Section 2 Simple Machines Chapter 12 The Lever Family, continued • Pulleys are modified levers. • The point in the middle of a pulley is like the fulcrum of a lever. • A single, fixed pulley has a mechanical advantage of 1. • Multiple pulleys are sometimes put together in a single unit called a block and tackle. • A wheel and axle is a lever or pulley connected to a shaft. • The steering wheel of a car, screwdrivers, and cranks are common wheel-and-axel machines.

9. Section 2 Simple Machines Chapter 12 Pulleys

10. Section 2 Simple Machines Chapter 12 Pulley

11. Section 2 Simple Machines Chapter 12 The Inclined Plane Family • Inclined planes multiply and redirect force. • An inclined plane turns a small input force into a large output force by spreading the work out over a large distance. • A wedge is a modified inclined plane. • A screw is an inclined plane wrapped around a cylinder.

12. Section 2 Simple Machines Chapter 12 Inclined Plane

13. Section 2 Simple Machines Chapter 12 Screws

14. Section 2 Simple Machines Chapter 12 Compound Machines • A machine made of more than one simple machine is called acompound machine. • Examples of compound machines are: • scissors, which use two first class levers joined at a common fulcrum • a car jack, which uses a lever in combination with a large screw