The point of this lab was to determine the coefficient of static and kinetic friction between wooden blocks and the surface of our lab tables. As I missed the first day of the lab, my report is in two parts. The first of which was done at home with the lab handout and improvised equitment
For the first part then, I up a did a number of tests with wooden blocks. First, I set up the blocks connected by a string to a cup which we slowly filled with water as shown:
We filled the cup until the block began to slide, and then repeated the process 3 more times, each time with one more block of equal weight stacked on top of the the rest of the blocks, thereby increasing normal force and in turn, static friction. We then plotted these values (normal force and mass of the cup/water) against eachother, obtaining this graph and chart:
This gives the value 0.3546 as the slope, which corresponds to the coefficient of static friction (since fs=us(n)).
In order to measure kinetic friction, we attached a force meter to the blocks and pulled them at a constant speed (or as near to it as possible) and thereby measured the average kinetic friction, again repeating the experement 3 more times with increasing weight. This when plotted yielded this chart and graph:
Giving us a slope of 0.2914, the equivalent of saying the coefficient of kinetic friction=0.2914
For our next experement we set up an aluminum track which we placed a wooden block of mass 0.273 kg and slowly increased the angle of until the block began to slide (which occured at theta=0.2443 rads), which allowed us to calculate the coefficient of static friction (us=0.2493). We then tilted the ramp to an angle of 0.4663 and allowed the block to slide while capturing its movement on a motion sensor. Which gave us this graph:
From this we calculated that Uk=0.370 (all calculations are below)
Finally, we were asked to predict the acceleration of the block if a hanging weight was attached to it, to calculate this (and the other two values above) we derived an equation as follows:
Giving us a value 2.81 m/s^2. We then tested our prediction by setting us a hanging weight attached to our block, we observed a value of a=2.695, which is approximately 4% less than our predicted value. This error is most likely due to slight deviations in angles and the actual friction between the block and the track, which changes depending on how rough/smooth the track is at an given point.
For the first part then, I up a did a number of tests with wooden blocks. First, I set up the blocks connected by a string to a cup which we slowly filled with water as shown:
In order to measure kinetic friction, we attached a force meter to the blocks and pulled them at a constant speed (or as near to it as possible) and thereby measured the average kinetic friction, again repeating the experement 3 more times with increasing weight. This when plotted yielded this chart and graph:
For our next experement we set up an aluminum track which we placed a wooden block of mass 0.273 kg and slowly increased the angle of until the block began to slide (which occured at theta=0.2443 rads), which allowed us to calculate the coefficient of static friction (us=0.2493). We then tilted the ramp to an angle of 0.4663 and allowed the block to slide while capturing its movement on a motion sensor. Which gave us this graph:
Finally, we were asked to predict the acceleration of the block if a hanging weight was attached to it, to calculate this (and the other two values above) we derived an equation as follows:
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