21-Sept-2016: Modeling Friction Forces

Lab 7 Modeling Friction Forces
Date: 21 September 2016
Lab Partner: Richard Mendoza, Mohammed Karim, Lynel Ornedo
Name: Andrew Martinez

Introduction: Conducting five different experiments that involve static and kinetic friction.

Apparatus:
- Wooden blocks
- Various mass plates
- String
- Wooden Panel
- Hanging mass
- Computer
- Ring Stand
- Focus Sensor
- LabPro
- Clamps
- Motion Detector

Procedure
Part 1: Static Friction
- Set up apparatus on uniform surface as shown adding weights for each block until it moves.
- Record the mass of each block until reach 4 and the weight it moved on
- Plot data into computer

Apparatus for part 1 with maximum number of blocks

Hanging Mass and pulley along with the string for tension

Blocks with tension from string

Part 2: Kinetic Friction
- Calibrate the force sensor
- Plug force sensor into LabPro and connect to computer via USB. Set to 10-N range
- Use 500-gram for calibration
- Find the mass of one of the wooden blocks
- Collect data from force sensor by moving the block horizontally at a constant speed along a uniform surface as LabPro
- Repeat till the last block
- Plot data and the slope gives the kinetic friction

Example of calibration of the force sensor

Part 3: Static Friction From a Sloped Surface
- Place the wood panel at an incline angle while leaving a block on it
- Raise until the block begins to move downward on its on
- Take the angle of that moment in order to help determine the coefficient of static friction

Part 4: Kinetic Friction From Sliding a Block Down an Incline
- Attach a motion sensor just above the wooden panel
- Leaving the Panel at the same incline find the coefficient of kinetic friction by using the motion sensor to find the acceleration.

Used for Part 3 & 4 to determine the static and kinetic friction. On top of the board is the motion sensor.

Part 5: Predicting the Acceleration of a Two-Mass System
- Use the kinetic friction you got from part 4 and derive an expression for the acceleration of a block with a hanging mass

Data:
Part 1
Block 1: 179.1 g
Block 2: 177.5 g
Block 3: 181.7 g
Block 4: 190.1 g
Hanging Mass
B1: 85 g
B1B2: 150 g

B1B2B3: 200 g
B1B2B3B4: 310 g

X:Normal Force vs Y:Force of static friction
By listing the normal force with its force of static friction we get our slope

Slope is .4106 making the coefficient of static .4106

Part 2

Using the data given by these charts plug there values into the Y for the graph below

With the Y from the graphs on top we can find the kinetic friction from the slope.
Uk = .2300

Part 3

Using the angel we found the block to move out we can determine the coefficient of static friction by substitution and plugging in.
Us = .4306

Part 4

Using the angel we found the block to move at and continue to move we can determine the coefficient of kinetic friction by substitution and free body diagram.
Uk = .2295

Part 5

Used Block 1 mass: 179.1 g hanging mass at B1: 85 g
Experimental a=2.068 m/s^2

Using the motion sensor then recording the acceleration the block moves out at the given masses.
Actual a(slope) = 1.682

Percent error: 22.94%

Conclusion: Aside from part 5 the experiments went according to plan. Part 5 has a large percent error due to human or systematic error. There could have been mistakes in which block was used or the pulley system was properly put in place or the motion sensor might have been placed to far. Whatever the case the majority of the experiment was a success and if part 5 were to be redone I am sure it would achieve more favorable results.