|
Forces of Friction II Lab
|
|
An Extension of Frictional Forces Lab Ivy Armstrong January 16, 2003 Purpose: To explore the forces of friction by testing the forces needed to get a mass moving and the forces that are needed to keep the mass at a constant velocity. I will test these forces by doing several trials of dragging a spool of wire along a vinyl ramp with different surfaces applied. Unfortunately because of the short length of the vinyl plank and inaccurate measuring equipment, the results will be inaccurate and in a science land we would have better luck at accurate results. Procedure: 1. Gather all of your materials, including a vinyl board, spool of wire, Newton scale, garbage bag box, and meter stick. 2.. Measure the length of the board and prop it up against the garbage bag box, measuring the height so you can, at a later time, find the angle from the horizontal. 3. Measure the force being applied on your wooden sleight in N. 4. Attach the spool of thread to your scale and lay it on the board, holding it stationary and then gently pulling on the Newton scale until the sleigh begins to move. Write down the force needed to move the spool from the stationary position. 5. Attach your spool to your Newton Scale and lay the spool at the bottom of the board. Pull the spool with a constant velocity up the board, writing down the force applied. 6. To do the data analysis you must figure out the Fn, and Ff by doing the calculations as illustrated below. 7. These values can be used in the friction equation to find the constant values of slope. 8. These slope values are used to compare forces of friction in constant velocity and static friction situations. Data: Constant Velocity Sleigh Weight (N) 4.25 N Trial 1 Vinyl Coated Wood Trial 2 Tin Foil Trial 3 Saran Wrap Trial 4 Wax Paper trial 1 trial 2 trial 3 trial 4 Fp (force of pull) 1. 75 3.0 2.5 1.5 Fp 2 (N) 2 4.0 2.25 1.0 Fp 3 (N) 1.75 3.5 2.5 1.0 Fp 4 (N) 1.75 3.0 2.5 1.5 Fp 5 (N) 1.75 3.5 2.5 1.5 Fp Avg 1.8 3.4 2.45 1.3 Length of ramp (cm) 122 122 122 122 Height of ramp (cm) 19 19 19 19 Angle of ramp (degrees) 8.85 8.85 8.85 8.85 STATIC trial 1 trial 2 trial 3 trial 4 Fp 1 (N) 1.5 3.75 2.0 .5 Fp 2 (N) 2.0 4.0 2.0 .5 Fp 3 (N) 1.75 4.0 2.0 .5 Fp 4 (N) 1.9 3.5 2.0 1.0 Fp 5 (N) 2.0 4.0 2.25 1.0 Fp Avg 1.83 3.85 2.05 .7 Sample Calculations: Calculating the angle of the ramp. Sin = height of the ramp Length of the ramp Sin =(19cm)/(122cm) Angle of ramp= 8.96 Finding the Fn. First you take your gravitational pull in N And split it into a triangle so that you have a side that is parallel to ramp. The angle that is formed by the floor and the ramp is equivalent to angle of the downward force and the force that is opposite of the Fn. Cos(ramp angle) = adjacent Hypotenuse cos8.96 = x/4.25 X= 4.2 N Table of Results: The colour section are what is included on the graphs. Constant Velocity trial 1 trial 2 trial 3 trial 4 Avg. Coefficient of Friction .429 .810 .583 .310 Static trial 1 trial 2 trial 3 trial 4 Avg Coefficient of Friction .436 .917 .488 .167 Sources of Error: 1. The Newton scale started at a location other than 0. There also was a spot where the needle tended to stick. Although, we still achieved consistence answers because they comparatively would be alright because they were all measured with the same scales. The problem can be solved by calibrating the scales correctly or purchasing higher quality equipment. 2. Splitters and particles that fall off the spool and ramp during the duration of our experiment cause the equipment to be ever changing and thus giving us a variance in the results. It is not a huge problem because these microscopic changes would not be apparent on the inaccurate measuring devices. This problem is not easily solved because this happens for all types of materials except our fun frictionless equipment in physics land. 3. Rips in materials that cover the board can account for some inaccuracy. This is hard to solve except if I were to get stronger materials in which to cover the board. Conclusion: In conclusion, the wax paper was the most frictionless surface that I tested. The constants were significantly lower when just starting to move the item versus keeping it at a constant motion. It shows that the force of friction really does vary depending on the surface. |