Learning Objective: Students will be able to explain how machines help to make work easier by calculating mechanical advantage to examine the relationship between the output force and input force.

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Learning Objective Students will be able to
explain how machines help to make work easier by
calculating mechanical advantage to examine the
relationship between the output force and input
force.
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POD

• Machine a device that makes doing work
  ___________________
• Input force the force that you _________________
  on a machine
•  
• Output force the force that the__________________
  _ applies

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POD

• Machine a device that makes doing work
  __easier____
• Input force the force that you __exert_________
  on a machine
•  
• Output force the force that the
  __machine________ applies

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• Mechanical advantage the number of times a
  machine increases the input force
• MA output force (in Newtons) / input force (in
  Newtons)
• MA Fout / Fin
• Output WORK is never greater than input work,
  BUT output FORCE can be greater than input force

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(No Transcript)
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Solution Steps Ask Yourself

• What do I know?
• What do I need to find out?
• What procedure am I going to use?
• How can I check my work?
• Notice when determining mechanical advantage,
  there is NO UNIT.

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Problem 1

• To open a bottle, you apply a force of 50 N to
  the bottle opener. The bottle opener applies a
  force of 775 N to the bottle cap. What is the
  mechanical advantage of the bottle opener?

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Problem 1 Answer

• To open a bottle, you apply a force of 50 N to
  the bottle opener. The bottle opener applies a
  force of 775 N to the bottle cap. What is the
  mechanical advantage of the bottle opener?
• Output Force / Input Force Mechanical Advantage
• 775N / 50N MA
• MA 15.5

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Problem 2

• To crack a pecan, you apply a force of 50 N to
  the nutcracker. The nutcracker applies a force
  of 150 N to the pecan. What is the mechanical
  advantage of the nutcracker?

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Problem 2 Answer

• To crack a pecan, you apply a force of 50 N to
  the nutcracker. The nutcracker applies a force
  of 150 N to the pecan. What is the mechanical
  advantage of the nutcracker?
• MA 3

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Problem 3

• To pull a weed out of a garden, you can apply a
  force of 50 N to the shovel. The shovel applies
  a force of 10 N to the weed. What is the MA of
  the shovel?

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Problem 3 Answer

• To pull a weed out of a garden, you can apply a
  force of 50 N to the shovel. The shovel applies
  a force of 10 N to the weed. What is the MA of
  the shovel?
• MA 1/5 .2

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Problem 4

• To pry a nail out of a wall, you can apply a
  force of 25 N to a hammer. The hammer applies a
  force of 650 N to the nail. What is the MA of
  the hammer?

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Problem 4 Answer

• To pry a nail out of a wall, you can apply a
  force of 25 N to a hammer. The hammer applies a
  force of 650 N to the nail. What is the MA of
  the hammer?
• MA 26

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Problem 5

• The mechanical advantage of a rope is 7. To lift
  a block on a movable pulley, you can apply a
  force of 100 N to a rope. How much force does
  the rope apply?

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Problem 5 Answer

• The mechanical advantage of a rope is 7. To lift
  a block on a movable pulley, you can apply a
  force of 100 N to a rope. How much force does
  the rope apply?
• Output Force 700 N

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Problem 6

• You are trying to pull apart two pieces of wood
  using a lever. The lever applies a force of 640 N
  to the weed with a mechanical advantage of 32.
  How much force must you apply to the lever?

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Problem 6 Answer

• You are trying to pull apart two pieces of wood
  using a lever. The lever applies a force of 640 N
  to the weed with a mechanical advantage of 32.
  How much force must you apply to the lever?
• Input Force 20 N

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Problem 7

• A wedge has a mechanical advantage of 20. To
  lift a refrigerator, you can apply a force of 30
  N to a wedge. How much force does the wedge
  apply?

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Problem 7 Answer

• A wedge has a mechanical advantage of 20. To
  lift a refrigerator, you can apply a force of 30
  N to a wedge. How much force does the wedge
  apply?
• Output Force 600 N

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Problem 8

• The output work of a machine is 35J. The input
  work is 70J. What is the efficiency of the
  machine?

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Problem 8 Answer

• The output work of a machine is 35J. The input
  work is 70J. What is the efficiency of the
  machine?
• Efficiency 50

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Problem 9

• The output work of a machine is 25 J. The
  efficiency of the machine is 100. What is the
  input work?

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Problem 10

• What type of machine is the one from the previous
  question?

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Problem 10 Answer

• What type of machine is the one from the previous
  question?
• It is an ideal machine (100 efficient)