# Mr. Johnson Perrysville Junior High Updated

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Mr. Johnson Perrysville Junior High Updated 2-3-2010
Simple Machines I use this presentation in my Technology class. This particular presentation is an adaptation of one that I had been using at the beginning of a unit I teach on simple machines. Though it was an ok presentation I had not employed many of the tools available in Power Point to jazz it up. In creating the new Simple Machines Presentation my hope is to be more attention getting, even fun in order to keep my audience interested. Images are of objects and machines that employ a particular simple machine, while they are also common objects. By making connections with common, familiar objects I want students thoughts to be spurred when they see these things at home. Also by using common objects I hope to increase students’ understanding through their prior knowledge, such as knowing what it feels like to use a wheel barrow when discussing 2nd class levers. Mr. Johnson Perrysville Junior High Updated

Terms To Know Work – done when an applied force causes an object to move in the direction of the force Energy – ability to cause change; speed, force, shape, or temperature Load – weight being moved Effort - force placed on an object that cause it to move.

What is a Simple Machine?
Tool used to make work easier Few moving parts Increased mechanical advantage Increase magnitude of out put force w/ cost of increased distance moved

Inclined Plane Inclined plane is a surface set at an angle, against a horizontal surface. Use less force over a longer distance to raise an object Object moves, not inclined plane More effort is needed to move an object up a steeper ramp. Effort is decreased with a longer ramp, but the trade off is moving the box a longer distance.

Wedge Similar to “Inclined Plane” Does work by moving
More acute the angle of the wedge, the more mechanical advantage it will have. The saw chain is what moves. Note – leading edge is not blunt but sharp, pointed “wedge” Examples: Airplane, & boat propeller, knife

Screw A screw is a helical inclined plane
A screw converts a rotational force, torque, into a linear force Used move material Invented by Archemedies (Archemedies Screw) Nuts, bolts, screws (machine, wood, drywall)

Pulley Used to change the direction of an applied force
Realize a mechanical advantage in either a linear or rotational system of motion. Pulleys change speed and force. Speed increases with a decrease in out put force.

Wheel and Axle Wheel & axles multiply the applied force OR distance traveled. Larger diameter wheels exert stronger forces on axles Before power steering was available for vehicles, larger diameter steering wheels were used to make turning easier

1st Class Lever fulcrum is located between the input effort and the output load Fulcrum = pivot point Fulcrum can be anywhere so long as it is between the applied force and load –does not have to be centered Fulcrum changes speed, in put and out put forces

2nd Class Lever fulcrum is at one end, and the applied force at the other, with the load in between Load moves the same direction as the applied force Example – wheel barrow

3rd Class Lever Input effort is higher than the output load
Applied force is between fulcrum and load Moves Faster Examples: fore arm, crane, mouse trap