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Simple Machines

This article provides an overview of simple machines, including levers, pulleys, wheel and axles, inclined planes, screws, wedges, and complex machines. It also discusses the concept of efficiency and includes calculations for mechanical advantage in different machines.

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Simple Machines

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  1. Simple Machines -a machine that does work with one movement

  2. Levers • A bar that is free to pivot, or turn, about a fixed point • Fulcrum- fixed point on the lever • Input arm- part of lever that person adds input force to • Output arm- part of lever that moves the output force or work

  3. 3 types of Levers

  4. First class lever • Fulcrum is located between the input force and the output force • screwdriver opening paint can • HW: 5 1st class levers

  5. Second class lever • Ouput force is located between the input force and the fulcrum • Wheel barrow Output force fulcrum Input force

  6. Third class lever • Input force is located between the output force and the fulcrum • Baseball bat, rake, hockey stick fulcrum Output arm Input arm

  7. Pulleys • Grooved wheel with a rope, chain, or cable running through the groove • Fixed pulleys • Change direction of force • Gravity Help!

  8. Movable Pulleys • Move when a force is applied. • Multiply the input force 2x.

  9. Pulley SystemsBlock and Tackle • A system of fixed and movable pulleys • MA = number of ropes supporting the weight • Do not count rope that you pull down on. • Do count a rope that you pull up on.

  10. MA of pulleys! 120 N 120 N 120 N 120 N

  11. Wheel and Axle • Two wheels of different sizes that rotate together • Can you think of any? • Doorknobs • Faucets • Steering wheel • Stereo volume knobs

  12. Inclined Planes • A sloping surface that reduces the amount of force needed to do work • Ramps • Roads

  13. Screw • Inclined plane wrapped around a cylindrical post • Wood screws • Soda lids • Olive jars

  14. Wedge • Inclined plane with one or two sloping sides that moves through an object or material to change the direction of the force. • Knives • Axes • Fullbacks

  15. Complex Machines • Two or more simple machines working together to perform a task • Scissors • Faucets • Bicycles

  16. Efficiency • Ability of a machine to use all of the work in. • E = output work/input work x 100% • Efficiency is reduced by friction. • Therefore always less than 100%

  17. Machines: Big Ideas • Change the way a person does work, not how much work is done. • Have: • Input work- effort put in • Output work- the work done by the machine • No machine can create work • Input work always greater than output work. • Due to friction

  18. Big Ideas contd. • Multiply input/our force • Screwdriver opening a paint can, wheel barrow • Multiply input distance • Rake, hockey stick • Change the direction of the input force. • Pulley

  19. Efficiency calculations • How efficient is a pulley system that requires 200J of input work to produce 150 J of output work? • What is the efficiency of a lever that requires 100 N of input force for 5 m? The work completed to move the bail of hay is 400 J.

  20. The End Calculations are next!

  21. Calculations • Calculate the Mechanical Advantage of a lever that has an input arm of 15 meters and a output arm of 3 meters. 15 m 3 m fulcrum

  22. MA of levers • MA = length of input arm length of output arm = 15 m 3 m = 5

  23. MA of a Wheel and axle • Calculate the MA of the door knob that you turn as you try to sneak into Mr. Miller’s room tardy. • The knob itself has a radius of 12 cm and the axle that runs through the knob as a radius of 1.2 cm.

  24. MA of W&A = radius of wheel radius of axle = 12 cm 1.2 cm = 10

  25. MA of an Inclined Plane • Calculate the mechanical advantage of an inclined plane/ramp used to load your ATV onto the bed of a truck. • The truck’s bed is exactly 2 meters off the ground and the ramp is 8 meters long.

  26. MA of I.P. = length of ramp height of ramp 8 m MA = 8 m 2 m = 4 2 m

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