Simple Machines Part 2

1
Simple Machines Part 2
2
6 Simple Machines

• Lever
• Wheel Axle
• Pulley
• Inclined Plane
• Wedge
• Screw

3
Inclined Plane

• Flat slopping surface in which an object can be
  pushed or pulled.
• Used to reduce the amount of effort needed to
  lift a load.

4
Geometry Definitions

• Angle theta
• Load R moved from point A to B.
• The height from point A to B is H

5
Geometry Definitions

• The length of the inclined surface is L
• The Effort (E) is applied parallel to the
  inclined plane

6
Formulas for inclined planes

• Mechanical AdvantageLoad / EffortE/R
• MA Length / Height L / H
• Only valid if Assuming no friction

7
Inclined Plane problem 1

• Given the diagram as shown, if L 12 inches, H
  3 inches and the effort is 30 pounds, find the
  mechanical advantage and the maximum load that
  can be moved.
• What is the tradeoff for reducing the effort?

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Inclined Plane problem 1, solution

• MA L/H 12in/3in. 4
• MA Load / Effort
• 4 Load / 30lbs
• Load 120lbs.

9
Wedge
10
Inclined plane vs. Wedge

• 2 major differences
• During use the inclined plane remains stationary.
  The effort is applied parallel to the slope.
• Wedge moves during use, the effort is applied to
  the vertical edge.

11
Shape of Wedges

• Only difference is the value of H.

12
Formula for Wedges

• Mechanical Advantage Load / Effort
• MA L / H

13
Wedge problem 1

• Find the mechanical advantage and the maximum
  separation load for a wedge with an incline
  length of 10 inches, an overall height of 4
  inches, and which is exerting an effort of 100
  pounds.

14
Wedge problem 1, solution

• MA L/H 10in./4in. 2.5
• MA Load / Effort
• 2.5 Load / 100lbs.
• Load 250 lbs.

15
Screw
16
Screw thread classification

• ¼ - 20 UNC
• ¼ is the outer diameter of the threads.
• 20 is the number of threads per inch
• UNC refers to Unified National Course.

17
Screw definitions

• Pitch is the distance between two adjacent
  threads.

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Screw pitch

• Pitch 1 / Number of threads per inch

19
Screw formulas

• Mechanical Advantage Load / Effort
• MA Circumference / Pitch C/P

20
Screw Problem 1

• A screw with 20 thread per inch is turned by a
  screwdriver having a handle diameter of 1 inch.
  What is the mechanical advantage of the screw?
• MA Circumference / Pitch C/P

21
Screw Problem 1, solution

• Circumference 3.141 1in 3.141 in.
• Pitch 1in./20 .05 in.
• MA C/P 3.141 in/.05 in 62.82