Sliding Friction. Taylor Gunderson, Steph Polasky, Lauren Seaman, Abby Fink. Mrs. Rudstrom, Concurrent Physics, Hour II.

Transcription

1 Sliding Taylor Gunderson, Steph Polasky, Lauren Seaman, Abby Fink Mrs. Rudstrom, Concurrent Physics, Hour II ovember, 0

2 Sliding : s of Introduction: The objective of this experiment was to determine the coefficient of sliding friction for wood on a desk, rubber-soled shoe on a dry desk, and a rubber-soled shoe on a wet desk. An electric force scale was used to collect data. It was hypothesized that the coefficient of friction for a shoe when dry will be higher than when wet, and theta the coefficient of friction and surface area are directly related. However, both of these hypotheses were not supported. Materials: One wood block Four one-kilogram weights A desk Access to water Paper towels One rubbed-soled shoe One force scale Computer LoggerPro computer system Methods:. Connect the force scale to the computer and open the corresponding folder in LoggerPro: Physics with Vernier.. Find the weight of the friction block using the force scale.. Record the weight of the friction block in the Data Table.. Attach the force scale to the friction block.. Set the friction block so the thin side is connecting with the desk. 6. Holding by the scale, pull the friction block horizontally along the desktop at a steady rate to ensure no acceleration. Record you results in the Data Table. 7. Add one kilogram of weight and repeat the procedure, filling out the information in the Data Table. Calculate the weight of the addition using the acceleration due to gravity. 8. Continue until Data Table is complete with a total of five trials. 9. Calculate the friction coefficient by dividing the friction force be the normal force. 0.Find the average value of the friction coefficients..using Excel, make a graph of " Force versus Force"..Repeat these steps for the wide side of the friction block, the shoe when dry, and the shoe when wet. Data:

3 Wood on Desk - Thin Side Block Weight, Force Virginia (Total High School Force, Concurrent Physics Shoe on Dry Desk Shoe Weight, Shoe on Wet Desk Shoe Weight, Wood on Desk - Thick Side Block

4 Analysis: The friction coefficient was found by dividing the friction force by the normal force. The average friction coefficient for wood slid on its thin side was 0.; for a shoe on a dry desk, 0.76; for a shoe on a wet floor, 0.76; for the wood when slid on its thick side, 0.9. The friction coefficient for the shoe on the dry floor was higher than the friction coefficient for the shoe on the wet floor. This refutes the hypothesis. It was likely lower due to the adhesive and cohesive properties of water molecules, which was not taken into consideration at the start of this lab. The change between the different tests of the wood was not significantly different, refuting the hypothesis. This is because the force per unit increases when the wood is placed on its thin side, leveling it out to if it was placed on its thick side. On the graphs below, the coefficient of friction is the slope. During this lab, mistakes could have been made due to human error. The same space used to drag the objects could have been different, the amount of water for the wet trials could have different, and the objects could have been pulled at different rates. Conclusion: In short, neither water nor increased surface area cause more friction to occur, meaning that the hypothesis was not supported. In the real world, tests such as

5 this could be used to determine the usefulness of certain tires over others, in the making of