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Physical Systems: Simple Machines

Physical Systems: Simple Machines. Simple Machines. Try this Take 20 sheets of paper and one staple Put the staple through the 20 sheets of paper – all at once Try it with a stapler A stapler is a system that is specifically designed to accomplish a task – stapling. Simple Machines.

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Physical Systems: Simple Machines

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  1. Physical Systems: Simple Machines

  2. Simple Machines • Try this • Take 20 sheets of paper and one staple • Put the staple through the 20 sheets of paper – all at once • Try it with a stapler • A stapler is a system that is specifically designed to accomplish a task – stapling

  3. Simple Machines • A stapler is a simple machine • A device composed of only one or two parts, that requires a single force to work • Most physical systems are made of one or more simple machines that work alone or together to make physical tasks such as nailing, cutting, throwing, carrying, chopping, and prying easier to do

  4. The 6 Simple Machines Screw Wedge Inclined Plane Pulley Wheel and Axle Lever

  5. Definitions: Energy: Ability to do work Work= Force x Distance Force: A Push or a Pull

  6. Inclined Plane

  7. Inclined Plane • The Egyptians used simple machines to build the pyramids. One method was to build a very long incline out of dirt that rose upward to the top of the pyramid very gently. The blocks of stone were placed on large logs (another type of simple machine - the wheel and axle) and pushed slowly up the long, gentle inclined plane to the top of the pyramid.

  8. Inclined Planes • An inclined plane is a flat surface that is higher on one end • Inclined planes make the work of moving things easier

  9. Screw Is a spiral staircase a screw?

  10. Wedges • Two inclined planes joined back to back. • Wedges are used to split things.

  11. Levers • A lever is a rigid bar that pivots at a point called the fulcrum • The load arm is the part of the bar between the fulcrum and the object (load) you want to move • The effort arm is the part of the bar between the fulcrum and where the effort is applied • Levers are designed so that the force applied to one part of the lever can be changed or redirected in order to move a load

  12. Levers • Input Force is the force applied by the user • Output Force is the redirected push that the lever applies to the load • Load Force is the force that the user’s input force has to overcome; sometimes referred to as resistance

  13. First Class Lever Fulcrum is between Input Force (effort) and Load Force (load)Effort moves farther than Resistance.Multiplies EF and changes its direction

  14. First Class Lever . • Common examples of first-class levers include crowbars, scissors, pliers, tin snips and seesaws.

  15. Second ClassLever Load Force (load) is between fulcrum and Input Force Effort moves farther than Resistance.Multiplies EF, but does not change its direction

  16. Second Class Lever • Examples of second-class levers include nut crackers, wheel barrows, doors, and bottle openers.

  17. Third Class Lever Input Force is between fulcrum and Load Force (load) Does not multiply force Resistance moves farther than Effort.Multiplies the distance the effort force travels

  18. Third Class Lever • Examples of third-class levers include tweezers, arm hammers, and shovels.

  19. Pulleys • Pulley are wheels and axles with a groove around the outside • A pulley needs a rope, chain or belt around the groove to make it do work

  20. Diagrams of Pulleys Fixed pulley: A fixed pulley changes the direction of a force; however, it does not create a mechanical advantage. Movable Pulley: The mechanical advantage of a moveable pulley is equal to the number of ropes that support the moveable pulley.

  21. COMBINED PULLEY • The effort needed to lift the load is less than half the weight of the load. • The main disadvantage is it travels a very long distance.

  22. WHEEL AND AXLE • The small diameter axle is stuck rigidly to a large diameter wheel. Fan blades are attached to the wheel. When the axel turns, the fan blades spin.

  23. Wheel and Axel • Using the wheel to turn the axle changes a small input force into a larger output force • Disadvantage is that the larger the wheel is, the further the force must travel along the wheel to create the output force • It is much easier to turn the wheel itself, than it is to turn the axle • Compare a car’s steering wheel to that of a bus or truck

  24. GEARS-Wheel and Axle • A modified wheel and axle • Toothed wheels • Used to speed up, slow down, or change direction of motion Small input gear – large output gear Large input gear – small output gear

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