STATIC EQUILIBRIUM

Skylur Jameson

2 April 2009

Experiment # 6

Purpose: The purpose of the experiment is to analyze a system that is in static equilibrium.

Equipment: Rod, clamps, pulleys, string, weights, weight holders, level, and protractor.

Discussion: The lab is designed to study the system in static equilibrium. In order for a system

to be in static equilibrium it will need to follow the equations:

∑ Fx = 0 and ∑ Fy = 0

By using each of these condition equations, we will be able to calculate the

unknown mass in a system that incorporates three different masses.

Procedure: To begin the experiment set up three different sets of masses, hanging each at

different heights, using the rods, clamps, and pulleys available. Also, in order to

have a successful experiment avoid the condition where m1 = m2. By eliminating

this case, our equipment will not be more accurate and helpful. To calculate the

angles of theta as well as the third elevators actual mass, use the free body

diagram and the equations:

m2*cosθ2 = m1*cosθ1 and m1*sinθ1 + m2*sinθ2 = m3

Lastly, in each trial run compare the calculated mass with the actual mass by

computing the percent error where the experiment minus theoretical is divided by

the experimental value.

Observations: The steel rods were touching the ground so that the system could hang below

the table. At times the elevators were quite wobbly. The pulleys were not

always at exactly equilibrium when were measured everything. The angle was

difficult to read because of the strings position to the table. The protractor could

have been read wrong because of the difficulty of reading it using the level. The

elevators were not below the table with the trials. Using the level helped

measure more accurate measurements. If a weight had more weight on it then

the angle was affected and the measure could have varied.

Conclusion: In conclusion, the experiment was very instructive and successful because it

helped explain how a system involving three different masses can be at static

equilibrium. After measuring the angles and weighing the masses used in the

system, we were able to calculate the theoretical mass as well as the percent

error present in each of the three trials occurring in the experiment. We found

that for each of our calculated masses for the third elevator were within the

range of less than five to the experimental mass for each mass. This led us to

have a percent error of 1.9, .06, and 2.1 percent for each corresponding trial. If I

had to add some criticism for the static equilibrium experiment would be that I

would have like to have done it alongside an experiment involving kinetic

equilibrium. In the end, I concluded that this experiment was one of the more

enjoyable experiments that we have done so far. It helped my understanding of

what exactly the different is between static and kinetic equilibrium.

Trial % error1 150 74 1.29 160 78 1.36 301 295 1.932 150 64 1.12 420 81 1.41 550 550 0.063 100 66 1.15 220 78 1.36 307 300 2.18

m1 (g) theta1 (degree) Radians1 m2 (g) theta2 (degree) Radians2 m3 calc. (g) m3 actual (g)

Trial % error1 ### 74 1.29 ### 78 1.36 301 295 1.932 ### 64 1.12 ### 81 1.41 550 550 0.063 ### 66 1.15 ### 78 1.36 307 300 2.18

m1 (g)theta1 (degree)Radians1m2 (g)theta2 (degree)Radians2 m3 calc. (g)m3 actual (g)