Forces at Equilibrium
Maram AlDukhayyil
ID# 201001719
Group members:
Maram AlDukhayyil
Asma Fadl Kayen
Section: 211
Submission date: 03-10-2012
PHYS 1411: Introductory Physics Lab
Lab Instructor: Nouf Al-Jalaud
Prince Mohammad Bin Fahd University
Fall 2012-2013
1. Abstract (Objective)
The experiment was about forces equilibrium. The main objective of this experiment
was about trying successfully balancing three objects with different masses. We found
that in order to achieve the balance status of those objects, the sum of the forces must
equal zero.
2. Theory
The theory that we used in this experiment was Newton’s second law. Which states
that the sum of the forced on a body is proportional to its acceleration. The
mathematical formulas used in calculations were:
1- (M1sinθ1+ M2sinθ1= M3), where
 M1sinθ1 is the first force multiplied by the Sin of its angel, and
 M2sinθ1 is the second force multiplied by the Sin of its angel.
 M3 refers to the fixed force.
2- Average Value: Sum of all trials\number of trials
3- Percentage Error: (|Approximate Value-Exact Value| / |Exact Value|) x
100%. Which approximate value refers to Average Value, and Exact Value
refers to M3.
3. Method
The methodology of working on the experiment was based on specific steps that
start first with a force table assembly. This force table assembly has three super pulley
clamps and 3 mass hangers all attached together by a string. Second, we brought 3
different masses “M1, M2 and M3.” M3 always had a fixed mass (25) and angle
(270°). The other two masses were different in each trial. After that, we started
adjusting the angles of M1 and M2 till we reached a state of equilibrium with the new
masses. Finally, we recorded the results and started the calculations.
4. Data
M3= 25 = at 270°
Trials
1
2
3
M1
30
20
40
θ1
45
38
352
sinθ1
.70
.61
-.10
M1sinθ1
21.2
12.31
-4.18
M2
20
20
50
θ2
166
144
143
sinθ2
.24
.58
.60
M2sinθ1
4.83
11.75
30.0
M3
26
24
25.9
5. Data Analysis (Results Discussion)
“M1sinθ1+ M2sinθ1= M3” we basically used this formula in order to get the final
answer for each trial. First, we recorded the mass and the angle for both M1 and M2.
After that, we calculated the Sin of each angel and multiplied it by its mass. Next, the
sum of M1sinθ1 and M2sinθ1 should be equal or close to the mass of the fixed force
“M3”, which is in this experiment was 25. Moreover, in order to find Average Value,
we have to find the sum of the final answers in all of the three trials and divide them
by 3. (26+24+25.9)/3 = 25.3. The final step in this experiment is to find the
2
Percentage Error. To do so, we used the following formula (|Approximate ValueExact Value) \ |Exact Value|) x 100 and our percentage error was 1.2%.
6. Conclusion
In conclusion, this experiment was about how could we balance forces to reach their
equilibrium level. I learned that in order to reach the equilibrium status, the sum of the
forces must be zero. That is why I should be careful in calculating the numbers and
changing the angels of the forces especially in this experiment.
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