# Chapter 15 : Simple and Compound Machines

### Topics covered in this snack-sized chapter:

#### Machine arrow_upward

• A machine is a tool that consists of one or more parts, and uses energy to achieve a particular goal.
• Machines are usually powered by mechanical, chemical, thermal, or electrical means, and are frequently motorized.
• Machines do not reduce the amount of work needed to perform a task; they reduce the effort needed from the user.

• #### Simple Machine arrow_upward

• A simple machine is a mechanical device that changes the direction or magnitude of a force.
• In general, they can be defined as the simplest mechanisms that provide mechanical advantage (also called leverage).

• ###### Simple Machines Work in One of 3 Ways

• Can take the force exerted by the individual and redirect it
• Can turn a small effort or force into a larger force (mechanical advantage)
• Can magnify the distance that a force acts on

• ###### Types of Simple Machines

• Lever
• Is a narrow beam that rotates around a single point called the fulcrum
• By placing an object to be moved, called the load, at one point on the beam and by applying an effort at another point the object can be moved more easily
• Inclined Plane
• Device designed to reduce the force needed to raise an object.
• For example, pushing a load up a ramp onto a platform requires less force than lifting the load onto the platform.

• Screw
• Screw is an inclined plane wrapped in a spiral around a shaft.

• Pulleys is a wheel over which a rope or belt is passed for the purpose of transmitting energy and doing work.

• Wheel and Axle
• An axle is a rod that goes through the wheel to create a wheel and axle machine
• Wheels and Axles are used to move and lift objects
• Some examples are: cars, wagons, doorknobs, pencil sharpeners, and bikes

#### Compound Machines arrow_upward

• A compound machine consists of two or more simple machines put together.
• In fact, most machines are compound machines.
• Compound machines can do more difficult jobs than simple machines alone.
• Their mechanical advantage is far greater, too.

• ###### Types of Compound Machines

1.

• There is a huge variety of compound machines available to assist with a large number of tasks.
• Several examples of compound machines include: bicycles, pliers, wheelbarrows and scissors.
• In bicycles, the pedals and wheels form cooperating wheel and axle systems, the brakes are levers and the parts are held together with multiple screws.
• Pliers are constructed with multiple levers. A wheelbarrow is a combination of a lever and wheel and axle. Scissors consist of two pivoting levers.

• #### Difference between Simple and Complex Machine arrow_upward

 Simple machine Complex machine A simple machine is what it says; it's a very simple machine, made up of only one simple machine, such as a screw or a lever. A complex machine is more than one simple machine working together, instead of working alone. The simple machine is one part. The complex machine is made up of different- different parts A simple machine is used to make work easier. A compound machine is two or more types of simple machines together. A simple machine is either a: lever, screw, incline, pulley, wheel and axle, and gear. A complex machine is made up of more than one simple machine.

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