Lab #7: Modeling Friction Forces

Modeling Friction Forces

Samuel
Ellis
Mia
9-21-2016

2. 

In this experiment, we tried to record data when perform some friction related experiments, and uses those data to calculate frictional force acting between object and surface

3. 

Theory: 1. Static frictions is the force acting between two bodies when they are not moving relative to one another. We tried to find the minimum static friction force that move object. If we place weights slowly and cautiously, then right before object is moving, that will be the minimum static force. Since the movement of an object require overcome static force, in this way we can know the minimum  force to overcome static force.
                 2. Kinetic friction as being proportional to the normal force, and independent of the area of the moving object. We used force sensor apply with constant force to collect data that that opposite force. In this case, it will be the kinetic friction force. 

4.

(1)

    1. Place the felt-side of the block on the lab table. Ties a string to the block and over a pulley at the end of the table.

    2. Patiently and slowly add weight to hanging weights. 

    3. Until block start sliding, remove the last weight you added.

    4. Record your data and repeat same procedure but with different mass of block.

    (2)
    1. Plug in a LabPro and connect it to computer with USB cable. Plug force sensor and switch it to 10-N range
    2. Weight the wooden block.
    3. Calibrate the force sensor using 500-grams hanging mess.
    4. Hold force sensor horizontally and zero the force sensor.
    5. Tie a string between force sensor and block. Click "Collect" and slowly pull force sensor horizontally.
    6. Repeat same procedure, but with different mass of block.

    (3) 

     1. Place a block on a horizontal surface.
     2. Slowly raise one end of the surface, tilting it until the block starts to slip.
     3. Use the angle at witch slipping just begin 

   (4)
    1. With motion detector at the top of an incline steep enough that a block will accelerate down the incline

    2. Measure the angle of the incline and the accelerate of the block.
    3. Determine the kinetic friction between block and surface from your measurement.

   5. & 6.

   (1)

    (2)

    m(block)          Kinetic Friction

    1. 180g             0.5507
    2. 320g             0.8970
    3. 520g             1.48
    4. 720g             2.13

   

    (3)

   

   (4)

   

  (5)

7. 

After we got our data from mass of the block and kinetic friction, we begin plug those number into LoggerPro. And used proportion fit to find the coefficient of kinetic friction. And we got 0.299+- .004. 

Since we placed block(s) on the incline plane and used motion detector to record data. We got position vs time & velocity vs time graph. And we highlight the area when the block start moving, then we use linear fit to velocity vs time to find its slope. And we got 1.462m/s.

8. 

The calculation from our data did not quite match with the data from computer. For instance, #4 we got 0.222 for kinetic friction. However, we received 0.2999 from LoggerPro. The reason for the difference is because maybe there have air-resistance or due to unbalance pull from people. And for #5, we got 1.81 from calculation. However, it show 1.46 in LoggerPro. The difference might due to adding of weights. Maybe because when we added weighs, we "drop" them too hard, which cause additional force to act on downward acceleration.