# Equilibrium Lab

Topics: Force, Mass, Pulley Pages: 2 (532 words) Published: March 6, 2013
February 25, 2013 Lab: Equilibrium of Forces
Purpose/Objective: The objective of this lab was to test the first condition of equilibrium for a set of concurrent coplanar forces, prove Lami’s Theorem, and to determine an unknown mass using rules of equilibrium. Procedure: In the lab, we wanted to find at what angles three separate weights would create a net zero force on a force table so that the ring holding the weights was exactly centered in the middle of the table. In Part 1, Set three pulleys at positions θ = 0, 120, and 240. We then had to determine the value of the weights w1, w2, and w3 that bring the system to equilibrium. In Part 2 we set three pulleys at positions θ = 0,110, and 260. We then had to determine the value of the weights w1, w2, and w3 that brings the system to equilibrium. In Part 3, we use an unknown mass as w3. We then had to determine the value of the weights w1 and w2, and angles θ2 and θ3 that brings the system to equilibrium. We then had to find the value of w3. Experimental Data:

Part 2
Force| Fn| θn| Fncos θ| Fnsin θ|
F1| 100N| 0| 100| 0|
F2| 205N| 110| -70| 193|
F3| 200N| 260| -35| -197|
∑Fx = -5∑Fy= -4
Part 3
Force| Fn| θn| Fncos θ| Fnsin θ|
F1| 100N| 0| 100| 0|
F2| 140N| 100| -24| 138|
F3| w3=?| 240| -76| -132|
∑Fx= 0 ∑Fy=-6

Calculations:

W3= (-100cos0 – 140cos100)/cos240
W3= (-100+24)/-.5
W3= 152N

Results:

Actual weight of w3= 160.29N

Percent error = 152-160.29 x 100 = 5.17%
160.29

Discussion:

Overall I think that our experiment was fairly successful with only a 5.17%. The weight that we got through our calculations came out to be 152 while the actual weight was 160.29. Also the sums of Fx and Fy should both net to zero and in our experiment we got pretty close with values of 0, -4, -5, and -6. There could have been many factors contributing to the percent...