# 1M20.40 - 1st, 2nd, and 3rd Class Levers

Code Number:
1M20.40
Demo Title:
1st, 2nd, and 3rd Class Levers
Condition:
Excellent
Principle:
Work and Power
Area of Study:
Mechanics
Equipment:
Fulcrum, eye-hooks, lead masses, lever arms, c-clamps.
Procedure:

Set up the 1st class lever with the fulcrum.  The mass can be moved to different positions on the 1st class lever.  A Newton scale can be used to show the force needed to lift the weights off of the table.  The 2nd and 3rd levers can be attached to the table with the c-clamp so that the pivot point doesn't move.  The masses can be moved to different points on the lever as can the eye-hooks.

NOTE: In the example we show in picture 2, it takes approximately 60 Newtons of force to raise a 24 Newton mass.

The crowbars come in several sizes.  Mechanical advantage increases with the length of the crowbar.

The socket and torque wrenches are used on a bolt screwed into a metal plate.  You can only tighten the bolt with the small socket, but can twist it off with the longer torque wrench.   There is also a larger bolt assembly that you can use quantitatively.  Tighten the nut onto the bolt to 100 Newtons using the small socket.  You can easily loosen the nut using only 30 to 30 Newtons using the longer torque wrench.

References:
• Paul Chagnon.  "Animated Displays III:  Mechanical Puzzles",  TPT, 32 January 1993.
• Mario Iona, "Levers for Premeds and Children", TPT, Vol. 229, #6, Sept. 1991, p. 354.
• G. Faucher, "Pushing or Pulling a Wheelbarrow", TPT, Vol. 27, #5, May 1989, p. 379.
• Igal Galili, "Pushing or Pulling", TPT, Vol. 29, # 3, March 1991, p. 134.
• Brion Patterson.  "Angular Momentum",  TPT, 566 October 1989.
• George W. Ficken, Jr., "Balancing a Tilting Canal Bridge", TPT, Vol. 26, # 8, Nov. 1988, p. 510.
• Fred Otto.  "Unlocking the Confusing World of Rotation",  TPT, p. 382 September 1988.
• Mark Carle.  "Olympic Wrestling and Angular Momentum",  TPT, p. 92 February 1988.
• Joseph E. Finck, "A Lever Arm Demonstration", TPT, Vol. 22, # 8, Nov. 1984, p. 538 - 539.
• Lora Wilhite, "Good Lessons from Simple Machines", TPT, Vol. 16, # 9, Dec. 1978, p. 645
• M-614:  "Croquet Mallet - Seesaw",  DICK and RAE Physics Demo Notebook.
• Martin Gardner, "The Unbreakable Match", Entertaining Science Experiments with Everyday Objects, p. 94.
• Vicki Cobb and Kathy Darling, "An Untearable Situation", Bet You Can't!, p. 34.
• Vicki Cobb and Kathy Darling, "No Pushover", Bet You Can't!, p. 32.
• Vicki Cobb and Kathy Darling, "Lower the Broom", Bet You Can't!, p. 31.
• Vicki Cobb and Kathy Darling, "A Match That's No Contest", Bet You Can't!, p. 30.
• Vicki Cobb and Kathy Darling, "A Pressing Problem", Bet You Can't!, p. 28.
• Janice VanCleave,  "Levers,"  Physics for Every Kid - 101 Easy Experiments in Motion, Heat, Light, Machines, and Sound.  pp. 118-119.
• Janice VanCleave, "Weakling,"  Physics for Every Kid - 101 Easy Experiments in Motion, Heat, Light, Machines, and Sound.  pp. 120-121.
• Janice VanCleave,  "Best Spot,"  Physics for Every Kid - 101 Easy Experiments in Motion, Heat, Light, Machines, and Sound.  pp. 122-123.
• Janice VanCleave,  "Lifter,"  Guide to More of the Best Science Fair Projects, p. 130.
• #170, "Lifter", Janice VanCleave's 203 Icy, Freezing, Frosty, Cool, and Wild Experiments.
• #171, "Longer", Janice VanCleave's 203 Icy, Freezing, Frosty, Cool, and Wild Experiments.
• #172, "Second-Class", Janice VanCleave's 203 Icy, Freezing, Frosty, Cool, and Wild Experiments.
• #173, "Ringer", Janice VanCleave's 203 Icy, Freezing, Frosty, Cool, and Wild Experiments.
• Curt Suplee, "Looking for leverage", Everyday Science Explained, National Geographic, p. 32.
• Curt Suplee, "Levers with Handles" Everyday Science Explained, National Geographic, p. 36.
• Curt Suplee, "Animals at work" Everyday Science Explained, National Geographic, p. 38.
• Borislaw Bilash II, “Wedges“, A Demo A Day – A Year of Physical Science Demonstrations, p. 260.
• Julius Sumner Miller, Q148 & A148, Millergrams II – Some More Enchanting Questions for Enquiring Minds, p. 30 & 88.

Disclaimer: These demonstrations are provided only for illustrative use by persons affiliated with The University of Iowa and only under the direction of a trained instructor or physicist.  The University of Iowa is not responsible for demonstrations performed by those using their own equipment or who choose to use this reference material for their own purpose.  The demonstrations included here are within the public domain and can be found in materials contained in libraries, bookstores, and through electronic sources.  Performing all or any portion of any of these demonstrations, with or without revisions not depicted here entails inherent risks.  These risks include, without limitation, bodily injury (and possibly death), including risks to health that may be temporary or permanent and that may exacerbate a pre-existing medical condition; and property loss or damage.  Anyone performing any part of these demonstrations, even with revisions, knowingly and voluntarily assumes all risks associated with them.