1. Thea De Guzman
2. Vector Addition and Static Equilibrium
3. Purpose
a. For this lab, the purpose is to use the MODELS for (1) vector addition and (2)
Newton’s conditions for static equilibrium in order to TEST PREDICTIONS
4. Apparatus – You need to use three strings positioned in a horizontal plane, three masses
suspended by pulleys, and calculators
5. Sample Calculations
a. See attached sheet
6. Data and Calculations
Case
1
2
3
m1
200g
300g
300g
Case
1
2
3
θ
30◦ N of W
37◦ N of W
45◦ S of W
Equilibrant Prediction
26◦ N of E 360g
3◦ S of W 361g
71◦ N of E 413g
m2
300g
200g
200g
β
60◦ S of W
53◦ S of E
65◦ S of E
Equilibrant Test
7. Summary
a. The purpose of this lab was to be able to use the math models for vector
equilibrium and Newton’s conditions to apply to static equilibrium. Using the
math models I was able to make our predictions for each of the three cases. For
the first case, I predicted that the results would be 360g and the direction would
be 26◦ North of East. My second prediction stated that the resultant would be 3◦
South of East and weight 361g. My final prediction said the resultant vector
would be 413g and 71◦ North of East. The method used to get the predictions was
first solving for the X and Y vectors by using Vx = Rcos(θ) and Vy=Rsin(θ). I
found the value of the resultant x and y by adding up all the other x and y
components separately and placing them appropriately in a new triangle. I used
the pathogen theorem to find the resultant and the law of sins or arc tan to find the
angle of diction.
8. B. Sources of Error are always present in lab and there are three types of error which are
human error, systemic error, and assumption error.
9.
a. Human Error – This may have occurred when reading the angles on the force
table incorrectly which will lead to a source of error.
b. Assumption Error – This may have occurred by assuming that the weights are
100% accurate.
c. Assumption Error – This may have occurred by assuming that there is no friction
in the pullies which apply more weight.