Materials: Force Board (only available in class), Protractor 
Time Allotment: 3 Class Days 
The purpose of this activity is to add three force vectors using a scaled vector addition diagram and to experimentally determine the resultant force for an object that is in a condition of static equilibrium; finally, you will use trigonometric functions to resolve the three forces into vector components and complete a mathematical analysis to show that the object is in a condition of static equilibrium.
In this lab, the forces acting upon a "point object" will be analyzed. The "point object" will be at rest and not accelerating. Thus, it would be expected that the "point object" satisfies the condition of static equilibrium. The diagram to the right depicts the actual classroom situation which will be analyzed.
B_{x} = _____________________ 
B_{y} = _____________________ 
C_{x} = _____________________ 
C_{y} = _____________________ 
The procedure for collecting data involves utilizing a "force board" to measure the magnitude and direction of three forces acting upon an object. The "center ring" is the object upon which the three forces act. The forces are the result of a chain pulled to a given tension (and measured by a spring scale). A protractor can be used to determine the direction of each force. It is best to align one of the scales in the direction of due east and to measure the other scales as counterclockwise angles of rotation from due East.

Magnitude (N) 
Direction (degrees) 
Force A 
_________________ 
_________________ 
Force B 
_________________ 
_________________ 
Force C 
_________________ 
_________________ 
Once the magnitudes and direction of the three forces are measured, use a separate page to construct a vector addition diagram and to determine the resultant force. The diagram should be a scaled drawing; the scale should be clearly indicated and the magnitude and direction of each vector should be clearly labeled. Label the magnitude and direction of the resultant on the diagram.
Use the trigonometric functions (as written in the PreLab section) to determine the horizontal and vertical components of each force. Show your work in each individual cell of the data table. List both magnitude and direction (north, south, east, west) for the components. Then, sum the individual components to determine the vector sum (last row).

Horizontal Component (N)* 
Vertical Component (N)* 
Force A 
_________________ 
_________________ 
Force B 
_________________ 
_________________ 
Force C 
_________________ 
_________________ 
Vector Sum 
_________________ 
_________________ 
* indicates "Please Show Your Work"
Using complete sentences, explain what is meant by static equilibrium and discuss the two methods which can be used to establish that an object is at static equilibrium. Do a bangup job!
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This page created by Tom Henderson and last updated on 8/7/97.