Name:
Lab Partner(s):
Date lab performed:
Dr. Julie J. Nazareth
Physics 121L/131L
Section:
Vector Properties of Forces
Part A (Do forces add like vectors?)
Table 1: Determination of the Equilibrant by Three Different Methods
Experimental
Graphical
Analytic
Magnitude**, S (g)
±
±
Angles, θ (°)
±
±
Part B (Predicting the equilibrant)
Table 2: Predict the Equilibrant by Two Methods and Verify Experimentally
Analytic
Graphical
Experimental Check
Magnitude**, S (g)
±
Angles, θ (°)
±
Part C (Breaking up a force into its components)
Table 3: Determination of the Components of the Equilibrant by Two Methods
Experimental
Analytic
x-component (θ=0°) magnitude**, Sx (g)
±
y-component (θ=90°) magnitude**, Sy (g)
±
** Note: Mass is not a vector quantity, but weight ( = mass * acceleration due to gravity) is. We
are simply using mass as a proxy for weight (a force), and saving ourselves the “trouble” of
multiplying all of our masses by the acceleration due to gravity at the earth’s surface. Please
round the mass to the nearest gram, and remember to include the mass of the weight hanger in
the total mass hanging off the string on the weight table.
Graphs: Show the determination of equilibrant for parts A & B on graph paper. Draw the
vectors you are adding head to tail (use the values given in the lab manual in parts A and B).
Draw the sum vector, S, from the origin to the head of the last vector in the sum. Measure the
length of the sum vector and use your scale to convert this length to grams. Use the protractor to
measure the direction (out of 360°) of your sum vector. The equilibrant, -S, has the same
magnitude, but the opposite direction of the sum vector. You do not have to draw in the
equilibrant vector on your graph. Write out your result for the equilibrant, -S, (magnitude with
units and direction out of 360°) at the bottom of your graph and draw a box around it so it is easy
to see. Remember: draw only one graph per sheet of graph paper; use most of the page to draw
your graph; put a word title at the top of the graph describing what is being shown; draw/state
your scale on your graph
Calculations: On a separate sheet of paper, show your calculations of equilibrant (parts A & B)
and the components of force (part C). Make sure you clearly labeled/title the calculations and
include units. Use the values given in the lab manual in parts A, B, and C. Remember, the
equilibrant, -S, has the same magnitude, but the opposite direction of the sum vector. Write out
your result for the equilibrant (magnitude with units and direction out of 360°) at the bottom of
your calculations and draw a box around it so it is easy to see.
Lab: Vector Properties of Forces
Data & Reporting score:
Updated 12/27/2008
Question: What are the sources of uncertainty in your graphically determined values? (State as
many as you can think of and be specific!) You may answer this question in the space below or
on an attached sheet of paper.
Don’t forget to write your summary! (After your introductory sentence (stating why you are
doing the lab), be sure to discuss the following: In all parts, do your results from the different
methods agree with each other within uncertainty? (If not, why not?); In part A, do your results
support or contradict the hypothesis that forces add like vectors? In part B, how well did you do
in predicting the equilibrant (how did the experimental check go)? In part C, do your analytical
values for the components of the equilibrant fall in the ranges that you determined
experimentally? Be specific in your discussions for parts A, B, and C.)
Lab: Vector Properties of Forces
Updated 12/27/2008