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Forces in Machines (Chapter 4)

Mr. Leavings. Forces in Machines (Chapter 4). What are we going to Learn?. Describe and Explain a simple machine Apply the concept of input force and output force Determine the mechanical advantage of different machines. Mechanical Systems and Machines. What is a machine?.

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Forces in Machines (Chapter 4)

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  1. Mr. Leavings Forces in Machines(Chapter 4)

  2. What are we going to Learn? • Describe and Explain a simple machine • Apply the concept of input force and output force • Determine the mechanical advantage of different machines

  3. Mechanical Systems and Machines What is a machine? A Device with moving parts that work together to accomplish a task.

  4. Input and Output The input includes everything you do to make the machine accomplish a task, like pushing on the bicycle pedals. The output is what the machine does for you, like going fast or climbing a steep hill

  5. Simple Machines A simple machine is an unpowered mechanical device, such as a lever.

  6. Mechanical Advantage Mechanical Advantage (MA): the ratio of output force to the input force. Foutput ____ MA = Finput

  7. Mechanical Advantage Lets do an example! On the board

  8. Levers Input and output forces for levers are related to the positioning of the fulcrum. Fulcrum

  9. Levers The Mechanical Advantage in a Lever is a ratio of the lengths of the input and output arms. If the input arm is 5 times the output then the MA is 5. Input Force/Arm Output Force/ Arm

  10. Levers There are three “classes” of levers. These are based on the location of the input and output in relation to the fulcrum. Fin Fout 1st Class Fin Fout 2nd Class Fout Fin 3rd Class

  11. Block and Tackle (pulleys) Ropes and strings carry tension forces along their length. They always act in the direction of the pulling force, this would be obvious if you ever tried to push a rope! The force in a rope is the same everywhere, if you cut a rope and insert a tension meter it would read the same at all points.

  12. Block and Tackle (pulleys) For each rope supporting the load it feels the force that you input. In this case you have two supporting ropes. Your input force is 5 N, what would the output force be? What is the Mechanical Advantage (MA)? Output: 10 N MA: 2

  13. Block and Tackle (pulleys)

  14. Gears Why are gears used in machines? The transmission of rotating motion from one place to another! You can transmit more force between gears than two smooth wheels because the teeth help prevent slippage.

  15. Gears The rule for how gears turn depends on the number of teeth in the gears. If one gear has 36 teeth and it turns once then an attached 12 tooth gear would have to turn 3 times to match the 36 teeth of the first gear. 12 teeth 36/12 = 3 turns 36 1 turn =36

  16. Gears Gear Turn Ratio Turns of output gear Number of teeth on input gear To=Ni Ti No Number of teeth on output gear Turns of input gear

  17. Gears

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