tech- lab

need_to_be_completed_.docx

Using four common lumber types that may be found in a 2”x4” size at a common building store we found that out of pine, fir, spruce, and cedar trees the fir tree two by four had the highest stressful load capability. Stress is defined as a force F divided by an area A, in the case of our experiment it is specifically a shear stress that caused the wood to split due to the force acting perpendicular to the anisotropic grain of the lumber. For the fir tree at the point of failure the digital hanging mass scale read a mass of 25 kilograms, then multiplying by the acceleration of gravity 9.8 meters per squared seconds resulted in a force of 245 Newtons. Dividing by an area of 3.39 squared millimeters resulted in a shear stress of 72.3 kN per squared meters. Then to test the accuracy of the digital hanging mass scale another stress was calculated for the fir lumber using the combined total masses that were placed on the scale at the point of failure which were read accurately by the scale at a total mass of 25 kilograms, however the 5-kilogram mass of the scale was not taken into account which results in a higher stress capability of 86.7 kN per squared meters. Due to the experiment resulting in two different maximum stress capabilities a percent difference of 7.2 percent was found, the more accurate stress capability being the higher one that included the mass of the scale; when using these values to decide which to use for a project we would recommend the stress that includes the scale mass. The maximum stresses for the rest of the lumber types are seen in Table 1.1 of Appendix A.

Lumber Type	Mass Added(kg)	Mass + Scale	Force(N)	Force w/scale	Stress Capability	Stress w/ scale
Fir	25	30	245	294	72271.39	86725.66
Pine	22	27	215.6	264.6	63598.82	78053.1
Spruce	20	25	196	245	57817.11	72271.39
Cedar	15	20	147	196	43362.83	57817.11

Table 1.1