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Mechanical Advantage

Mechanical Advantage. MA tells how much easier it is to use a simple machine than to not use it. Huh? (translation, please!). Mechanical Advantage (MA). You have a choice between two simple machines. One is easier to use than another. You will choose the one that is easier to use, right?

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Mechanical Advantage

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  1. Mechanical Advantage • MA tells how much easier it is to use a simple machine than to not use it. • Huh? (translation, please!)

  2. Mechanical Advantage (MA) • You have a choice between two simple machines. One is easier to use than another. You will choose the one that is easier to use, right? • MA is a property of simple machines that quantifies what we mean by “easier”.

  3. Simple Machine Work Work Simple Machine Force D F Distance Conservation of Energy Remember: Work = Force x Distance

  4. Conclusions • Work into a machine equals work out of a machine. • Simple machines do not make work go away. They make work easier to do by making the input force less, for example. • You don’t get something for nothing. You must “pay” for the reduced input force by moving greater distances.

  5. Example: Inclined plane • You need to move a box from the floor to a table, 1 meter off the floor. • You can raise the box with just your muscles (no simple machine). You push with 50 N of force. • W = F x d; W = 50 N x 1 m = 50 Nm • If you use a 5 meter inclined plane, you push with only 10 N to move the box up the ramp. • W = F x d; W = 10 N x 5 m = 50 Nm

  6. F Distance Simple Machine Force D F = input force (Fi) Force = (Fo) Distance = input distance (di) D = (do) Quantifying Mechanical Advantage Input side Output side So, using the forces only, MA is the ratio of output force over input force.

  7. Quantifying MA • MA = Fo / Fi • To easily remember this, think of a phrase using 2 words that begins with fo______ and fi_________. • How about food fight?

  8. Problem A force of 200 N is applied to a machine in order to lift a 1,000-newton load. What is the mechanical advantage of the machine?

  9. Answer MA = Fo / Fi MA = 1000 N / 200 N MA = 5 Notice that the answer doesn’t have any units. Why?

  10. Problem 1 1. A machine is designed to push an object with a weight of 12 N. If the input force for the machine is set at 4 N, what is the mechanical advantage of the machine?

  11. Answer 1 1. MA = 3

  12. Problem 2 2. A machine is required to produce an output force of 600 N. If the machine has a mechanical advantage of 6, what input force must be applied to the machine?

  13. Answer 2 2. Fi = 100 N

  14. Problem 3 3. An input force of 35 N is applied to a machine with a mechanical advantage of 0.75. What is the size of the load this machine could lift (how large is the output force)?

  15. Answer 3 3. Fo = 26.25 N

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