Lab Partners’ Names: __________________________
__________________________
__________________________
Period________
APC Physics Lab: Newton’s First Law for Vector Addition Applied to Bodies in Equilibrium
Purpose: To demonstrate Newton’s First Law of Motion for a stationary body through the use of
vector addition both graphically and by component.
Testable Question: Will the vector sum of forces acting on a motionless body (a body in
equilibrium) add up to ZERO both by graphical and component addition?
Research: Text book or other sources:
o Newton’s First Law of Motion as it pertains to motionless bodies
o Vector addition and Resultants
Discussion: (expectations): By adding together the vector forces acting on a stationary
body, a resultant force of zero (no resultant) should be obtained.
Procedure:
o Set up equipment as shown below.
o Obtain the data sheet (each student has their own data sheet) and:
o Tape data sheet to table so as not to move
o Trace force wheel on paper
o Mark a dot on paper where center of force wheel is
o Hang weights (no less than 200 grams on any cord) off table over pulleys so that
wheel stays stationary
o Trace the three string directions when wheel comes to rest
o With one string set a 0 degrees, measure and record angles between strings on data
table and on data sheet.
o Record gram-force acting on each string on both the data table and on data sheet.
o Decide on and record the scale you are using for the gram-force vectors
o Convert the line tracings into scaled vectors
o Add the scaled vectors together head-to-tail using a protractor and ruler, making
sure not to change their direction or scaled length when moving and adding them.
o Draw and label the resultant of your vector addition
o Measure your resultant length and convert to the gram-force it represents, recording
this force on your data sheet and in your data table.
o Calculate the x- and y- components of the two vectors that are not at 0o and record
their values along with the vector at zero degrees in the table.
o Add the x- and y- components together.
o Use the x- and y-components to find a resultant value.
o Compare this resultant to the graphically-found resultant using a percent Difference
calculation.
o ATTACH your original data sheet to your lab so that it folds out easily for
measurement by me
Stationary knot
Force
Wheel
Mass
1
Mass
3
Mass
2
Materials:
o Paper, force wheel, protractor, metric ruler, string, three 500 gram spring scales, tape,
various weights (no less than 200 g on any string)
Data: Scale used to represent vectors:
1 cm = ________ grams
Length of Graphical Addition Resultant vector: _______ cm = _______ grams
Vector
Angles
Gramforce
used
(g)
Length of
Vector
(cm)
Calculated Calculated Calculated
xyResultant
component component
(cm)
(cm)
(cm)
0o
Total of x- and y- components
Sample Calculations:
Quantity
Vector gram force
conversion to length
Resultant Length
Conversion to gram
force
Calculated
x-component
Calculated
y-component
Calculated
Resultant
Formula
Substitution
Answer
Units
Conclusion Questions:
1. What does it mean if you got a resultant vector measurement greater than zero?
2. How close were your graphical and vector component addition resultants? Indicate this with a
calculation of % Difference: (SHOW the calculation and comment on it…)
% Difference = |One value – Average of Values| (100)
Average of Values
3. What can you briefly say about the merit/detriments of each method of vector addition?
Vector
Merits
Detriments
Addition
Style
Graphical
Method
Sum of
Component
Method