Friction Lab Name: L1

Transcription

1 Friction Lab Name: L1

2 Introduction The coefficient of friction is defined as the ratio between the force needed to move an object and the normal force. In equation form: µ = f / F n. Normal force refers to the supporting surface force and is often equal to the objects weight Procedure Part 1 Determining coefficients of friction on a flat surface Devise a procedure to (a) determine the static coefficient of friction for a block sliding on a horizontal board. (b) determine the kinetic coefficient of friction for a block on a horizontal board. The static coefficient is determined from the force to start the object moving, and the kinetic coefficient is determined from the force to keep the object moving at a steady speed. Part 2 Slipping on an inclined Board Using the same board from part 1, place the block on the board and tilt it until the box just begins to slide. Using a meterstick, make the proper measurements to be used to determine the angle at which slipping occurred Part 3 Testing factors which affect coefficient of friction Devise experimental procedures to determine the factors which affect the static coefficient of friction. Factors to try are: a) weight of object b) surface area of contact c) type of surface object slides on Be sure to only test one variable at a time while keeping all others constant. Use as much variety in your measurements as possible and display your data in concise form. Use at least three different variations of each factor. L2

3 Friction Lab Name: When turning in the lab, only turn in from this page forward. The prior pages are for your reference only Partners: Procedure: Briefly summarize the general procedures and data needed in order to determine: (a) the coefficient of static friction of an object on a surface (b) the coefficient of kinetic friction of an object on a surface L3

4 Analysis Part 1 Determining u k and u s on a flat surface (a) Draw a FBD of the block and the forces acting on it (b) Data For u s For u k Total mass (kg) Normal Pulling Static Friction max (N) Total mass (kg) Normal Pulling Kinetic Friction (N) (c) Calculations Using the above data, determine the value of u s and u k showing all work. u s u k L4

5 Part 2 Slipping on an incline (a) Draw a FBD of the block and the forces acting on it (b) Data Length A Length C Total Mass A C (c) Calculations I.) Determine the slipping angle θ of the incline, show work II.) Using the formula, µ s = tan θ, determine µ s III.) Make a Fnet(x) equation and solve for the fs(max). Make a Fnet(y) equation and solve for the Fn. Use these results to determine µ s, show all work. IV.) Compare the answers to parts II and III above. V.) Compare the value of µ s found in this section to the one found in Part 1 on the flat surface; comment on your results L5

6 Part 3 Analysis of factors that affect the coefficient of friction Section A Investigation of weight changes on coefficient of static friction Surface used block on board Surface area used large flat side of block Mass varied Trial Mass (kg) including block F N (N) f s (N) u s Section B Investigation of surface area changes on coefficient of static friction Surface used block on board Surface area varied Mass constant Trial Surface Area Description Mass (kg) including block F N (N) f s (N) u s Section C Investigation of surface type changes on coefficient of static friction Surface used varied Surface area large flat side Mass constant Trial Surface Type Description Mass (kg) including block F N (N) f s (N) u s L6

7 Final Conclusion Write a conclusion for part 3 explaining what factors affect the coefficient of static friction. Clearly state your conclusions based on your hard data. ***ALSO, based on your knowledge of the coefficient of friction, you should have an understanding of what to expect prior to doing this lab experiment. If your data is not what you expected, clearly state that you believe your data to be misleading, why you think that, and the results that you would expect to observe. L7