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1 From: WHAT IS A SIMPLE MACHINE? SIMPLE MACHINES, WORK, FORCE, ENERGY, AND NEWTON'S THREE LAWS OF MOTION 1. SIMPLE MACHINES help us make better use of our muscle power to do WORK. 2. A Machine produces FORCE and controls the direction of Force, it cannot create ENERGY. 3. Simple Machines help us lift, pull, increase elevation of heavy things, change the direction of the force, increase the force, split things, fasten things, and cut things. 4. We all use simple machines everyday, opening a door, turning on the water faucet, going up stairs, or opening a can of paint. 5. Bottom Line: They are Simple Tools used to make Work easier. THE SIX SIMPLE MACHINES ARE: 1. The Lever 2. The Inclined Plane 3. The Wedge 4. The Screw 5. The Wheel and Axle 6. The Pulley HISTORY 1. What do you think the first Simple Machine was? 2. Throughout history, people have learned ways to increase Force, change the direction of Force, and increase the rate of Work. 3. We don't actually know what the first Simple Machine was, but it was probably a large stick used to move heavy objects (Rocks). The Lever. 4. Or it could be the sharp rock they used to scrape animal skins, the wedge. 5. Logs were use early in modern building to move huge rocks by rolling them along. These logs became the Wheel and Axle around 3000 B.C., and were one of the most important inventions in history. 6. The Inclined Plane and Rollers were used in building the Great Egypt Pyramids, one of The Seven Wonders of the World. 2.5 Million Limestone blocks were moved hundreds of miles over 20 years, weighing 2 to 70 tons each. Ramps over one mile long were required to place stones. 1

2 7. The Lever, Rollers and Pulleys were use to build Stonehenge, England. 8. Throughout all the early civilizations, including, Lebanon, Peru, Bolivia, and Easter Island, Simple Machines were used to build magnificent buildings. In Lebanon Temples were built with blocks 64 feet long and 13 feet wide, weighing 1,200 tons apiece, a Force of 25,000 men was required to raise one stone. The Lever, Rollers, Pulleys, Wedges, and the Screw were all used early in history. 9. The Industrial Revolution, which in Great Britain in the 1700s, was sparked by the invention of the Steam Engine. The Industrial Revolution helped bring people into the machine age and vastly increased the availability of many kinds of products. 10. Machines enable people to do Work with LESS Muscle Effort and with Greater Speed. WORK 1. What is the Science Definition of Work? 2. You are doing Work when you use a Force to cause Motion. 3. Motion is the changing of position of an object in Reference to a Starting Point. 4. Work is the transfer of Energy through motion. 5. In order for work to take place, a Force must be exerted through a distance. 6. Amount of Work (w) done depends on two things: A. The amount of Force (F) exerted. B. The Distance (d) over which the Force is applied. 7. Equation for Work - w = F x d 8. Work is measured Joules (N-m) after British Scientist James Prescott Joule 9. One Joule = N-m, is Work done when a Force of one Newton acts through a Distance of one Meter. 10. There are two factors to keep in mind when deciding whether work is being done: A. Something has to move. B. The motion must be in the direction of the applied Force. 10. The amount of Work a machine produces equals the Force used Multiplied By the Distance the Machine lifts or moves and object. 11. How does a Simple Machine make Work easier? A. Transferring the Force from one place to another. 2

3 B. Changing the direction of a Force C. Increasing the magnitude of a Force D. Increasing the distance or speed of a Force 12. What do you need to do Work Energy, Energy is the ability to do work. FORCE 1. A Force is a PUSH or a PULL, that causes a change in the motion or shape of an object. SAMPLES: Push open a door, or Shove a book across a desk, or the PULL of Gravity on a ball when you drop it. 2. Words to think about that use Force pushing, pulling, stretching, squeezing, bending, and falling. 3. Forces can be equal holding a book up in your palm of your hand, or a book laying on the table Balanced Forces Your hand or the table pushes up and the book pushes down. 4. Some types of Forces; Gravity, Electricity, Magnetism, and Friction. 5. Whenever an object is caused to move, whether from a standstill or while already in motion, a Force is required. 6. Gravity is a Universal Force. Gravitational Force causes every object to attract every other object; Ball fall to the ground; The moon orbiting the Earth. Every object in the universe exerts a force on every other object, and that force is Gravity. 7. Friction is a Force that opposes motion. Friction occurs when two substances rub together. Rub your hands together, what did you feel? Why? Heat is a byproduct of Friction. 8. The motion of objects is reduced because of Friction. Why you stop swing on a swing, why a ball stops rolling. 9. Friction can be reduced by smoothing and polishing the surface of contact, by lubricating surfaces with grease or oil, or by using roller instead of sliding. 10. Sometimes we want to increase Frictional Forces When using the brakes on a bike or car, we are increasing friction in order to stop. 11. If there were no Friction, your life would be much different. You wouldn't be able to walk (think about walking on ice) or hold things between your fingers. You wouldn't be able to turn the pages of a book, or keep your shoes tied, or stop your car with the brakes. 12. What do you call the Force of Gravity on your Mass? WEIGH! Remember? 13. Two important factors dealing with force are: Mass and Distance, The Earth hold you because its mass is so large compared to yours, but you do not feel the gravity pull of your neighbor sitting next to you! 3

4 14. Force in the SI is measured in Newton and is part of the equation for Work! W = F x d. THE LEVER 1. One of the earliest and simplest of machines, a large stick would work as a lever to move huge rocks. 2. The Lever is essentially a Rigid Bar that is free to turn about a Fixed Point called the Fulcrum. 3. Ever Lever has three (3) parts: A. Resistance Force or Load, What you are trying to move or lift. B. Effort Force - The Work done on the Lever. C. Fulcrum A fixed pivot point. 4. Levers are divided into Three Classes depending on the position of the Effort, Resistance, and Fulcrum. FREE. A. FIRST CLASS LEVERS - FREE 4

5 1) The Fulcrum (fixed pivot point) is located between the Effort and the Resistance Forces. A SEESAW. 2) The Effort and the resistance move in opposite directions. The Effort Down in order to Lift the Resistance or Load. 3) When the Fulcrum is closer to the Effort than to the Resistance, there is a Loss in Force but a Gain in Speed and Distance. 4) When the Fulcrum is closer to the Resistance than to the Effort, there is a Loss in Speed and Distance, but a Gain in Force. 5) When the fulcrum is Midway between the Effort and the Resistance, there is no change in Force, Speed or Distance. 6) Samples of First Class Levers Seesaw, Crowbars, Scissors, and Claw Hammers. B. SECOND CLASS LEVERS - FREE 1) The Resistance is between the Effort and the Fulcrum. 2) The Fulcrum is at one End of the Lever. 3) The Fulcrum is usually closer to the Resistance, (load). 4) Second Class Levers produce a gain in Force. Openers, and NutCrackers. 5) Samples of Second Class Levers Wheelbarrow, Bottle C. THIRD CLASS LEVERS - FREE 1) The Effort is Between the Resistance and the Fulcrum. 2) There is usually a loss in Force, but a gain in Speed and Distance. 3) Samples of Third Class Levers Broom, Shovel, Fishing Pole, Baseball Bat, and Tongs. INCLINED PLANE 5

6 1. An INCLINE PLANE is a Sloping Surface used to lift heavy loads with relative little Effort. The Incline Plane does not MOVE. 2. A surface that is raised at one end. 3. An Inclined Plane provides for NOT Less Work but Less Effort. The trade off is Greater Distance to Travel. 4. Allows you to lift a weigh you normally couldn't lift to a Higher Level, Sample Barrels. 5. Increase the elevation of heavy objects without having to lift the object directly. 6 (wrong). LIFTING A BARREL OR ROLLING A BARREL UP AN INCLINED PLANE A. LIFTING - The Force needed is equal to the weigh of the barrel multiplied by the height of the platform. 100 lb barrel up 5 m, force equals 100 lb x 5 m = 500 N. B. ROLLING The Force equals weigh of barrel multiplied by the height of the platform, divided by the distance of the Inclined Plane 10 m, Force equals 100 lb x 5 m / 10m = 50 N. [Notes from Harlow on Step 6 above. This is WRONG WRONG WRONG! First of all, lb, meaning pounds has no place in a discussion which uses the proper metric units of N for force, kg for mass, m/s 2 for acceleration, and J for energy or work. Let us assume that the barrel has a mass of 25 kg, as is indicated in the diagram (though it incorrectly says effort instead of mass). Also, the diagram shows that rolling requires an effort of 10 kg, meaning, I suppose, that the mechanical advantage is 10/25, so the length of the ramp is 25/10 = 2.5 times the height. Let s assume the ramp has a length of 10 m, and a height of 4 m. Then the correction to 6 above is: 6

7 6 (corrected). LIFTING A BARREL OR ROLLING A BARREL UP AN INCLINED PLANE A. LIFTING - The Force needed is equal to the mass of the barrel multiplied by the acceleration due to gravity. 25 kg times 10 m/s 2 makes 250 N, which is the barrel s weight. Lifting the barrel straight up a distance of 4 m, requires work equal to 250 N times 4 m = 1000 J. B. ROLLING The Force equals weight of barrel multiplied by the height of the platform, divided by the distance of the Inclined Plane 10 m, Force equals 250 N x 4 m / 10m = 100 N. Rolling this barrel up the ramp requires work equal to 100 N times 10 m = 1000 J, which is the same amount of work as lifting. The ramp does not reduce the work done, it just spreads the force out over a larger distance.] 7. Samples of Inclined Planes Simple Ramp, Escalator, Stairs, Ship Plank, and Ladder. THE WEDGE 1. A Wedge is a form of the Inclined Plane which is used to increase Force. With a Wedge, The material (log) remains in place while he Wedge Moves through it. 2. A Wedge can be one sloping surface, a Single Incline Plane, like a doorstop. Or two sloping surfaces, a Double Incline Plane, like the Wedge used to split wood for the fireplace. 3. Wedges can be Forced between two things to hold them tightly together, like nails or a doorstop. 4. When Sharpened the Wedge becomes either a knife or and ax blade. The tip of a Screwdriver (other than Philips) is a simple Wedge. 5. Wedges can be used to split, cut or fasten. 6. Samples of Wedges Ax Head, Log Spliter, Chisel, Knife, Nails, Doorstop, Plows, Tip of Screwdriver, Scissors, Needles, and Pins. THE SCREW 7

8 1. The Screw is another form of an Inclined Plane. 2. The Screw is an Inclined Plane Wrapped in a spiral around a Cylinder Post. 3. A Screw has two (2) parts: A. The Body Cylinder Post B. The Thread Inclined Plane wrapped around the cylinder. 4. When thinking about a Screw think about anything that has Threads. 5. If you look closely at the Screw, you'll see that the threads form a tiny RAMP that runs around the Screw from the tip to near the top. 6. The Pitch of a Screw is the Distance between two consecutive threads. 7. One function of the Screw is to Fasten Things the Standard Screw or Nuts & Blots. 8. Drill Bits are a Screw used to make holes. 9. A Jackscrew is used to Lift heavy objects. Car Jack. 10. Airplane Propellers, Helicopter Blades, and Fan Blades are Screws that screw through the air. 11. Propellers on Boats Screw through the water. 12. Most every machine built requires the use of some form of Screw to Fasten it together. 13. Imagine you are driving a Screw into a Board. As you turn the Screw, the Threads seem to PULL the Screw into the wood. The Wood seems to SLIDE up the Inclined Plane. Actually, the Plane Slides through the wood. THE WHEEL AND AXLE 8

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10 1. The Wheel and Axle was first used around 3000 B.C. and is one of the most important invention in history. 2. The Wheel and Axle is a Wheel connected to a rigid pole. 3. Rollers were the forerunner the Wheel, several logs placed under heavy object. 4. The Wheel and Axle is basically a modified Lever, the Center of the Axle serves as a Fulcrum making the Wheel a Lever that rotates around in a circle. 5. Effort Force is applied to a large Wheel to Turn the Smaller Axle. 6. Samples of Wheel and Axle - Door Knobs, Screwdrivers (the whole screwdriver), Water Faucets, Handle Bars on a Bike, Airplane Propellers, Helicopter Blades, Fan Blades, Wheels on a Car, Wagon, Bike (or anything). 7. Gears are a modified or special Wheel and Axle. 8. A Gear is a Wheel with Teeth along its circumference. 9. Effort is exerted on one of the gears, causing the other gear to turn. 10. In most gears, the larger gear is the Effort Gear turning a much smaller Gear the Resistance. 11. Samples of Gears Bike Sprockets, Can Opener, Gears in any machine. ENERGY 1. ENERGY is the ability to do WORK to cause something to MOVE. 2. ENERGY is the ability to cause CHANGE. 3. Energy can be found in several forms, CHEMICAL and MECHANICAL. 4. Living things cannot work without Energy, and machines cannot work without Energy. 5. You cannot get no more Work out of a Machine then the ENERGY you put into it. Due to FRICTION, the WORK produced is usually less than the Energy used. 6. Forms of ENERGY can be transferred from one form to another, but Energy cannot be created or destroyed. The use of Energy and the lost of Energy usually ends up as HEAT. 7. Forms of Energy, Solar, Electrical, Heat, Light, Chemical, Mechanical, Wind, Water, Muscles, and Nuclear. 8. All Energy Originates from our SUN. Our number one source of Energy. 9. There are TWO Types of Energy: 10

11 A. Potential Energy - Energy of Position or Stored Energy. B. Kinetic Energy - Energy of Motion. 10. Potential Energy is Stored Energy, or Energy of Position. 11. Anything may have Stored Energy that gives it the Potential to cause change if certain conditions are met. 12. The Amount of Potential Energy a sample of matter has depends on its Position or Condition. 13. A Flowerpot sitting on the ledge two stories up has Potential Energy because it could Fall due to Gravity. 14. Potential Energy due to Height above the Earth's surface is called Gravitational Potential Energy. 15. The Greater the Height the Greater the Potential Energy. 16. Springs in Toys is another sample of Potential Energy. 17. Potential Energy is Changed to Kinetic Energy upon movement. 18. Kinetic Energy is Energy in the Form of Motion. 19. The Greater the MASS of a Moving Object, the More Kinetic Energy it has. 20. Mechanical Energy is the Total amount of Kinetic and Potential Energy in a System. 21. Energy is always conserved Law of Conservation of Energy, Energy may change from one form to another, but it cannot be created or destroyed. 11