Wheel and Axle

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Wheel and Axle
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2nd class lever

• Is the MA gt or lt 1?
• Since the distance LE is gt than LR it is greater
  than 1.

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Example

• Steering Wheel
• Larger the wheel the greater the mechanical
  advantage.
• Disadvantage
• Hands have to travel a longer distance

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3rd class lever

• What about MA?
• MA lt 1

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Example

• The larger the wheel diameter, the lower the MA.
  The more work its take for the motor to turn the
  wheel.
• Advantage Speed of the wheel will increase.

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Formula for wheel and axle

• MA R / E
• MA Radius to Effort / Radius to Load
• MA LE / LR

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Wheel Axle Problem 1

• Suppose a wheel with a 12 inch radius is used to
  turn a water valve stem of radius .5 inches.
  What is the MA.
• MA LE / LR 12 in. / .5 in. 24

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Wheel Axle Problem 2

• Consider an axle used to drive the wheels of a
  car. The wheel radius is 15 inches, while the
  axle radius in 1 inch. What is the MA?
• MA LE / LR 1inch / 15 inch .067

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Wheel Axle Rotary to linear
S

• Rotary motion has been change to linear motion as
  the wheel moves.

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Wheel Axle Rotary to linear
S

• S Distance traveled in one revolution
• Circumference of the wheel
• Pi wheel diameter
• 3.141 D

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Wheel Axle Problem 3

• You have a choice of putting a 26 inch diameter
  tire or a 30 inch diameter tire on your bicycle.
• Which tire will increase top speed of the bike.
• How much will the speed change in percent.

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Wheel Axle Problem 3 answer

• S 3.141 26 inches 81.666 inches.
• S 3.141 30 inches 94.23 inches.
• change((94.23-81.66)/81.66))100
• 15.4 speed increase.

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Pulley
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Pulley

• Adaptation of the wheel axle.
• Change the direction of motion
• And/or reduce the effort needed.

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Pulleys work

• Work at the effort end Work at the load end
• Effort Dist. Traveled by the rope Load
  dist. Moved by the load.

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Pulley Formulas

• MA R/E
• MA The number of strands supporting the load.
  The end strand ONLY counts when the effort is
  pointing upwards.

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3 types of pulleys

• Fixed Pulley
• Fixed to a strong stationary member.
• The effort and the load are equal.
• If the load is lifted 1 ft. then the rope needs
  to move 1 ft.
• MA 1
• End strand is not counted because it is pointing
  down.

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3 types of pulleys

• Movable Pulley
• Attached to the moving load.
• Effort is ½ the load.
• If the load is lifted 1 ft., the rope needs to be
  pulled 2 ft.
• MA 2
• End strand is counted.

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3 types of pulleys

• Block Tackle
• Use of 3 pulleys.
• Effort is 1/3 the load.
• If load is lifted 1ft. It takes 3 ft. of rope to
  lift it.
• 75lb load take 25lbs of effort.
• MA 3

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Pulley example 1

• The pulley system show is used to lift a load of
  60 lbs. a distance of 2 feet. How much effort
  must be applied, and how much rope do you need to
  pull.

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Pulley example 1

• MA 6
• MA R/E
• 6 60 / effort
• Effort 10 lbs.
• Distance 2ft. 6
• Distance traveled 12