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Simple Machines

Simple Machines. Mechanical Advantage. Ideal Mechanical Advantage:. Is the mechanical advantage of an “ideal machine” Theoretical value The IMA for a pulley is equal to the number of supporting ropes. Ex #1.

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Simple Machines

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  1. Simple Machines Mechanical Advantage

  2. Ideal Mechanical Advantage: • Is the mechanical advantage of an “ideal machine” • Theoretical value • The IMA for a pulley is equal to the number of supporting ropes.

  3. Ex #1 A lever is used to move a rock. The resistance distance if 20cm and the effort distance is 120cm. What is the IMA?

  4. Ex #2 A lever has an IMA of 5. Find the distance the effort arm must be pushed down in order to lift a 5kg mass 25cm up.

  5. Ex #3

  6. Ex #4 Calculate the IMA for each simple machine.

  7. Actual Mechanical Advantage: • Is the mechanical advantage of a real machine • Actual value • IMA will always be higher than AMA due to friction.

  8. Lifting an object, AMA will always be less than IMA because working against gravity • But if you are lowering an object, AMA will be greater than IMA because gravity (friction) is helping

  9. Ex #5 To move a rock with a weight of 100N, an effort force of 18N is needed. If a lever is used, calculate the AMA.

  10. Ex #6 A lever with an AMA of 4 is used to lift mass of 5kg. How much effort force is needed?

  11. For a machine to be 100% efficient: • IMA = AMA • So…

  12. Ex #7 A ramp is used to slide a 350kg piano onto the back of a pickup truck. a) Calculate the IMA b) Calculate the AMA c) Is this 100% efficient?

  13. Not 100% efficient b/c IMA = AMA

  14. Ex #8 A crowbar is used as a lever to pry a board loose. A boy applies an effort force at a distance of 0.8m from the fulcrum. The resistance force acts 0.2m from the fulcrum. a) Calculate the IMA. b) Assuming friction is negligible, what is the resistance force if the boy pushes with a force of 225N?

  15. IMA = AMA

  16. Ex #9 You need to lift a 100kg load by applying a force less than 980N. Ignoring friction, which of the following machines should NOT be chosen?

  17. 1. 2. 3. 4.

  18. Ex #10 The great pyramid of Cheops is 146m high. Workers used large stones to build this structure, each with a mass of 900kg. Egyptologists believe that ramps were used to raise the stones to the height needed. It is thought that 6 workers, each pushing with 400N of force, could accomplish this task. Neglecting friction, what would be the length of the ramp needed to get each stone to the top of the pyramid?

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