FIRST QTR LAB
READING TO DO:
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L4 -
TITLE:
CONCURRENT VECTORS – The Law of Equilibrium
TEXT: p92-97.
All lab reports must start with your name and physics class section. Next the TITLE
of the lab, and then the 7 SECTIONS BELOW. Please staple your report.
PURPOSE OF LAB
“To attempt to prove the law of equilibrium for three concurrent forces acting on a
ring (and to obtain a percent discrepancy for forces in both the X & Y directions)”
METHOD
a)Avoid the case of three 120 degree angles, or where one angle is too small.
b)For best results, all three spring scales should read between 10 and 18 newtons.
c)Construct a neat vector diagram; use a protractor to accurately measure <1 & <2.
d)With pencil, ruler, & protractor, redo and enlarge this diagram, using a scale so
that vector lengths represent their actual values in newtons; label diagram fully.
DATA
a)Set F3 pointing West on the X-axis, and follow the directions on the board.
b)Carefully record the readings for F1, F2, & F3 in newtons & the values of <1 & <2.
EQUATIONS & CALCULATIONS
EQUATIONS: The sum of all X Forces must = 0, AND the sum of all Y Forces must = 0.
Use the sine & cosine of the two measured angles 1 & 2 to find the four components.
Find X & Y components of F1 & F2, & along with F3, test the above law mathematically.
CHART OF RESULTS
The X and Y components of F1 & F2, the sum of the forces for both the X and Y
directions, and two % discrepancy results, one for the X and one for the Y forces.
(In % discrepancy formula denominators should be an average of the two values used.)
DISCUSSION OF RESULTS & CONCLUSIONS:
Discuss your results, their accuracy, and the lab experiment in general. Evaluate
whether you've achieved all the parts of the purpose of the lab, explain any problems
encountered, and draw your final conclusions regarding the purpose of the experiment.
QUESTIONS TO ANSWER: (on the last page of the lab report)
Define in complete sentences: Concurrent, component, equilibrant, law of equilibrium.
BACKGROUND INFORMATION:
1)An object is in translational EQUILIBRIUM when it is at rest, OR moving in a
straight line at a constant speed.
2)THE LAW OF EQUILIBRIUM is a corollary of Newton's first law of motion. It states:
"When an object is in translational equilibrium, the vector sum of all forces
acting upon it must equal zero." This means that all forces acting on the object
are cancelled by other equal but opposite forces. Since all forces have
horizontal(X) and vertical(Y) components, the sum of the X Forces acting on it
must equal zero, AND the sum of the Y Forces acting on it must equal zero."