75%(4)3 out of 4 people found this document helpful
This preview shows page 3 - 4 out of 4 pages.
Determine the critical angle for the wooden cart to be on the verge of sliding down the inclined plane:ΣF = ma = 0Experimental θ = 35.8°mgsinθ = μmgcosθμs= sinθ / cosθμs= tanθtan-1(0.88) = 41.3°Discussion:In Part I, we determined that the cork surface had the largest friction coefficient. This is consistent with my experiences because in general, cork is rougher than felt and plastic. As the roughness between two surfaces increases, so does the coefficient of friction. From the graph we can determine a number of things. At A, it is clear to see that there is a large force being applied. This is the force that is used to overcome the static friction. At B, the object is experiencing maximum static friction. At C, the force is smaller due to the fact that the object has overcome static friction and is experiencing kinetic friction. Finally, at D, the object is moving at constant velocity and is still experiencing kinetic friction. The normal force does not affect either the coefficient of static or kinetic friction. The coefficient (μ) is a constant number between two surfaces. However, the normal force does affect the frictional force. The frictional force (Ffr) = μFN. The pattern between the values of the coefficients of static and kinetic friction is that the coefficient of static friction is always greater than the coefficient of kinetic friction. In Part II, thetheoretical value of the critical angle is 41.3° whereas, the experimental value of the critical angle is 35.8°. This corresponds to a 13.3% error. Sources of error in this lab included human errors such as when determining the experimental angle. This angle was determined by pushing the slope higher until the block moved down the hill. There is a large inaccuracy in the angle doing it using this method.FNFfrmgsinθmgcosθ
Conclusion:Doing this lab we determined the various values of friction when comparing it to different surfaces. From the experiment we can conclude that the friction of the felt < friction of plastic< friction of the cork surfaces.