Presentation on theme: "Mr. Johnson Perrysville Junior High Updated"— Presentation transcript:
1 Mr. Johnson Perrysville Junior High Updated 2-3-2010 Simple MachinesI 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
2 Terms To KnowWork – done when an applied force causes an object to move in the direction of the forceEnergy – ability to cause change; speed, force, shape, or temperatureLoad – weight being movedEffort - force placed on an object that cause it to move.
3 What is a Simple Machine? Tool used to make work easierFew moving partsIncreased mechanical advantageIncrease magnitude of out put force w/ cost of increased distance moved
4 Inclined PlaneInclined plane is a surface set at an angle, against a horizontal surface.Use less force over a longer distance to raise an objectObject moves, not inclined planeMore 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.
5 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
6 Screw A screw is a helical inclined plane A screw converts a rotational force, torque, into a linear forceUsed move materialInvented by Archemedies (Archemedies Screw)Nuts, bolts, screws (machine, wood, drywall)
7 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.
8 Wheel and AxleWheel & axles multiply the applied force OR distance traveled.Larger diameter wheels exert stronger forces on axlesBefore power steering was available for vehicles, larger diameter steering wheels were used to make turning easier
9 1st Class Leverfulcrum is located between the input effort and the output loadFulcrum = pivot pointFulcrum can be anywhere so long as it is between the applied force and load –does not have to be centeredFulcrum changes speed, in put and out put forces
10 2nd Class Leverfulcrum is at one end, and the applied force at the other, with the load in betweenLoad moves the same direction as the applied forceExample – wheel barrow
11 3rd Class Lever Input effort is higher than the output load Applied force is between fulcrum and loadMoves FasterExamples: fore arm, crane, mouse trap