Wheel and Axle Lever Simple Machines Pulley Screw Wedge Inclined Plane
Why are they Useful? Simple machines are useful because they can make a physical job easier by changing the amount or the direction of the force exerted to do work.
Machine – a tool that helps us do work Machines help us by: Changing the amount of force on an object. Changing the direction of the force.
Example: I push a bookshelf to move it. Force is a push or pull. Example: I push a bookshelf to move it.
Energy is the ability to do work. Example: I must have energy to run the mile.
Work is the result of force moving an object. Example – Picking up something heavy is hard work!
Load the weight that is moved, lifted, or supported by a simple machine. Load
Inclined Planes
Inclined Plane – a slanted surface to make lifting easier Examples: ramp, stairs
What is an Inclined Plane? A ramp is an inclined plane. A ramp helps move objects from one level to another - - higher or lower.
An Inclined Plane is a simple machine that helps reduce the force needed to move a load. Instead of picking up this load and lifting it straight upwards, the load can be pushed along an elevated plane, which changes the direction of the force. The user must move the load a greater distance, but the force needed to move it will be less.
Pulleys
What is a Pulley? A pulley is a simple machine with a wheel and a rope. The rope fits around the edge of the wheel. You can use a pulley to move a load up, down or sideways.
A pulley is made of rope or string wound around a wheel to change the direction of a force.
Examples of where pulleys can be used: Flag Poles Sailboat Blinds Crane Curtains Fishing Pole
Pulley – a simple machine consisting of a wheel with a groove for a rope. Fixed pulley is anchored to a single spot. It can rotate but does not move up or down. Moveable pulley is free to move up and down. Pulley system is a group of two or more pulleys that work together to lift a load.
The pulley does not move Single Fixed Pulley This pulley lets the user change the direction of the force, allowing someone to pull down to lift the load up. The effort needed to lift this load is equal to the weight of the load. This is because the load is supported by only 1 rope arm. You must also pull an amount of rope equal to the height you wish to lift the load
Single Moveable Pulley The pulley moves This pulley system requires only half the effort needed to lift the weight of the load. If the load weighs 20 lbs, only 10 lbs of effort is needed to lift it. The load is supported by 2 rope arms under the pulley. Each load arm supports half the weight of the load, so the arm pulling up uses only 10 lbs of effort to lift this load. You must pull twice as much rope as desired to lift the load a certain height. Example: Pull 2 ft of rope for each 1 foot of height that you want to lift the load.
Single Fixed/Single Moveable Pulley This pulley system combines the properties of their single components into a system that changes both the direction of the force and the amount of force needed to lift the load.
More supporting ropes = less force required to lift an object 1 2 3 4 More supporting ropes = less force required to lift an object
Supporting rope arms only pull up, not down. 1 2 3 4 Supporting rope arms only pull up, not down.
Supporting rope arms only pull up, not down. 1 2 3 4 Supporting rope arms only pull up, not down.
Simple Machines allow users to accomplish work more easily!