Pulleys Simple Machines Six types A simple machine

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Pulleys

Pulleys

Simple Machines: Six types A simple machine is a mechanical device that changes the

Simple Machines: Six types 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 use mechanical advantage (also called leverage) to multiply force Inclined Plane We’re going to focus on pulleys today! Screw Pulley Lever Wedge Wheel and Axle

How do pulleys make work easier? • They help move things to higher places

How do pulleys make work easier? • They help move things to higher places with much less effort. – Imagine how much effort would be involved if a person had to climb to the top of a flagpole every day to hang a flag.

Parts of a pulley Wheel Axle Groove F = Force, or the amount of

Parts of a pulley Wheel Axle Groove F = Force, or the amount of work it takes to move something L = Load, or the weight of the object you are moving

Types of pulleys The more compound the pulley, the greater the mechanical advantage. What

Types of pulleys The more compound the pulley, the greater the mechanical advantage. What is mechanical advantage? We’ll cover that in the next slide.

Mechanical advantage A simple way to think of mechanical advantage of a pulley is

Mechanical advantage A simple way to think of mechanical advantage of a pulley is to count the number of rope sections that support whatever object you are lifting (not counting the rope that is attached to the effort). In this diagram, what is the mechanical advantage for: A? B? C?

Mechanical advantage, cont. Notice that as mechanical advantage increases, the amount of rope needed

Mechanical advantage, cont. Notice that as mechanical advantage increases, the amount of rope needed also increases. So, they payoff is less effort required but over a greater area. MA=1 MA=2 MA=3

Activity: Pulley towers! • In this activity you will use your building skills to

Activity: Pulley towers! • In this activity you will use your building skills to build a tower that can support a pulley. • We will then compete to see whose tower can support the most weight lifted by the pulley. – Rules: • Limited supply of sticks & glue • Tower must be at least 3 craft sticks tall

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