To use graphical and mathematical means to find conditions for Translational Equilibrium.


The resultant of two forces acting at the same point on a body is that single force whose effect on the body is the same as the combined effects of the two forces. If the two forces at an angle, the resultant is equal to the diagonal of the force parallelogram of which the two forces are the sides. The equilibrant of two or more forces is the single force that can produce equilibrium with them. It is therefore equal but opposite to the resultant.


  1. Each person in your lab group must read every page in this online procedure. Along the way, there will be questions that you must answer.
  2. Designate one person in your group as the Data Recorder. This person should open the Google document Experiment 5 - Composition of Forces for the approved answer template.
  3. When this Google document opens, sign in to your Google account.
  4. From theFILE Menu, chooseMake a copy...
  5. From theFILE Menu, chooseRename...and rename the document as follows: Exp 5 - Period (1, 3, 6, or 8) - Group #.
  6. Share this document with the members of your group and with Mr. Skubis at HSTScience@gmail.com.
  7. As a group, answer all questions. Remember to use complete sentences and be mindful of grammar, spelling, and punctuation.
  8. As an individual, you will complete Calculation Requirements as specified below.
  9. Finally, AS A GROUP write a CONCLUSION as described at the end of this lab. Submit the conclusion on the Google document for full credit.
  10. REMEMBER: **Plagiarism** is a form of **Academic Dishonesty** which carries harsh consequences. DO YOUR OWN WORK!


  1. Obtain a force table apparatus and the iron ring to which is attached 3 pieces of string.
  2. Place the ring over the center post of the table and lay the string over the separated table pulleys.
    (For ease, make sure one of the pulley strings coincides with 0o. The remaining strings should be relatively equiangular.)
  3. Attach a minimum of 200 g and a maximum of 500 g to each of the outstretched strings.
  4. Observe the position of the iron ring over the center post. When the force system is in equilibrium the post should be as close to the center as possible.
  5. Place additional masses on the appropriate string(s) to achieve equilibrium.
  6. Finally, name the vectors as A, B, and C where Force C is the equilibrant of A and B.
  7. Record the total mass on each string and the angles between them.
  8. Each group member should do their own trial. Make sure each trial has different angles and masses.

Calculation Requirements

As an individual, draw and submit a properly scaled vector diagram that depicts YOUR DATA. You must also prepare a handwritten document that shows ALL calculations that pertain to YOUR DATA in this experiment. This document must be neatly written on looseleaf paper or word-processed. NO FRAYED EDGES. For this experiment, that means you need to show the COMPLETE trigonometric calculations including each error necessary to complete the Calculations Table on the Google Doc.

You should follow the format: ANALYZE, PLAN, COMPUTE, EVALUATE.

In the PLAN stage, be sure you show all the Algebra and Trigonometry involved with solving the problems.

In the COMPUTE stage, include the actual experimental data with their proper SI units and show how they plug into the equation. Be sure your answer has 3 sig figs and proper SI units (if applicable).


Graphical Method of Analysis

To find the resultant of A and B graphically, a vector diagram must be constructed as illustrated.

  1. Determine a convenient scale such that the diagram fills a sheet of paper. Draw forces A, B, and C making sure their respective lengths are to scale and the angle between them is as you recorded.
  2. Using the parallel lines drawing device, construct a parallelogram around forces A and B. The diagonal of this parallelogram is the resultant of A and B and should be labeled C'.
  3. Starting from point P, force C" is the same magnitude as C but opposite in direction.
  4. The difference in magnitude between C'P and C"P is the graphic magnitude error. The difference between Microsoft_WordScreenSnapz001_14-13-30.jpgand Microsoft_WordScreenSnapz002.jpg is the graphic direction error. Record each value in the appropriate table.

Mathematical Method of Analysis

  1. Calculate the magnitude of C'P using the known values of AP, BP, and PreviewScreenSnapz001.jpg.
  2. Now calculate the value of Microsoft_WordScreenSnapz001_14-13-30.jpg.
  3. Determine the calculated magnitude and direction errors as you did previously.

Your Individual Responsibility

Every person in the group is responsible for:

  1. Complete and labeled diagram
  2. Complete calculations (3 sig figs, proper SI units, no frayed edges.)