Resultant and Equilibrium Forces (Stephen Herr)

: Resultant and Equilibrium Forces

Principle(s) Investigated

  • Newton's 2nd Law
  • resultant 
  • equlibrant
  • equilibrium
  • Vector Addition

Standards : (not complete yet)
1.Scientific progress is made by asking meaningful questions and conducting careful investigations. As a basis for understanding this concept and addressing the content in the other four strands, students should develop their own questions and perform investigations. Students will:
a. Select and use appropriate tools and technology (such as computer-linked probes, spreadsheets, and graphing calculators) to perform tests, collect data, analyze relationships, and display data.
b. Identify and communicate sources of unavoidable experimental error.
c. Identify possible reasons for inconsistent results, such as sources of error or uncontrolled conditions.
d. Formulate explanations by using logic and evidence.
e. Solve scientific problems by using quadratic equations and simple trigonometric, exponential, and logarithmic functions.
f. Distinguish between hypothesis and theory as scientific terms.
g. Recognize the usefulness and limitations of models and theories as scientific representations of reality.
j. Recognize the issues of statistical variability and the need for controlled tests.
k. Recognize the cumulative nature of scientific evidence.


Graph paper, fishing line, masses, pulleys, ring stands, scissors, protractor, ruler, pen, scales, 


  1. place a mark at the center of the graph paper
  2. tape the paper to the center of a level desk
  3. tie three spring scales to a washer with fishing line
  4. attach weights to the scales and hang them one rate edge of the desk
  5. adjust the paper and scales so the washer is over the center dot on the a paper
  6. record the direction of each of the forces and their magnitude using an appropriate scale
  7. complete a parallelogram by using any two of the forces and draw a diagonal line between them.  This is the sum of the two vectors, and is known as the equilibrate.

Student prior knowledge:



Will be added latter.

Questions & Answers: 

1.  What is the net force on the washer if it is not moving?

Applications to Everyday Life: