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Understanding Simple Machines and Mechanical Advantage

Learn about the principles of simple machines such as wedges, levers, pulleys, and hydraulic presses. Discover how to calculate mechanical advantages and efficiencies to optimize work output. Explore concepts like inclined planes and screw jacks. Real-life examples demonstrate the application of these machines.

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Understanding Simple Machines and Mechanical Advantage

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  1. Chapter 6 Simple Machines

  2. Simple Machines • Wedge • Cam • Screw • Lever • Pulley • Wheel & Axle • Hydraulic press

  3. Black Box Machine • Use input force to do work • Ideal Machine – input work equals to output work (no losses) • We can change the amount of force needed to do the work

  4. Inclined plane • Pushing a box up inclined plane with incline angle  (no friction) • Lift straight up • Using inclined plane • Hence reduced force needed • But

  5. How to characterize Machine? • Ideal Mechanical Advantage • Geometrical construction • Ratio of output force to input force for ideal machine • Can get IMA of 30-100 or more • Jack & chain hoist

  6. Back to Inclined plane • Pushing a box up inclined plane with incline angle  (no friction) • Lift straight up • Using inclined plane • Hence reduced force needed • But

  7. Actual Mechanical Advantage • Energy losses in machine • Define AMA:

  8. Efficiency of Machine • How “good” is a given machine? • In terms of power

  9. Example—Pulley Systems 20 kg load can be lifted with 65 N force. Pulling rope 150 cm lifts load 30 cm. Find IMA, AMA, Eff?

  10. More simple machines • Wedge • Screw Jack (cam r, pitch p) • Lever (Fulcrum) • Pulley • Hydraulic press

  11. Example If it takes 100 ft-lb of torque to tighten an engine bolt. How long should the wrench be if 60 lb of force is applied?

  12. More on Pulley Systems • IMA of a block and tackle equals to the number of strands supporting the moving block.

  13. Example—Pulley Systems 20 kg load can be lifted with 65 N force. Pulling rope 150 cm lifts load 30 cm. Find IMA, AMA, Eff? How many strand?

  14. Example A pulley can lift 5000 N using 1000 N force. If the IMA is 20, what is the efficiency of the system?

  15. Hydraulic Press • Volume fixed (cross-section area A) • IMA • Almost no losses

  16. Example Compressed air furnishes a force of 60 N to the 0.8 cm^2 area of an oil line that is used to lift a piston in a car lift. What must be the cross sectional area to be able to lift 1100kg vehicle?

  17. Combining machines • Machines in series • Output of 1st is the input of 2nd, etc. • Break 2x2

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