Students will use an experiment to determine the static friction coefficient of an object.
Lab:
The students assembled a lab setup that would allow them to measure the static friction coefficient of an object with a table. The accomplished this with a pulley, string, a cup, and a wooden block with felt on one side.
The mass that will be used to determine the static friction coefficient is the wooden block so the mass of the block was measured so that the students would be able to calculate the normal force that the table would have on the block.
Then the components are assembled as shown:
The block is placed on the table with the felt side down and a string is tied to it. the string is then looped on a frictionless*, massless* pulley and the other end is tied to a cup.
Once the setup is complete the students then took the following steps. They added water to the cup until just the point when the block would start moving. They then measured the mass of the cup and water. The students repeated these steps five times. Each time with an added block to increase the mass and therefore the Normal and ultimately the frictional force the block would have with the table.
The Mass of the block(s), the mass of the water+cup, and the Normal force between the table and the block was recorded and kept track of in a table:
The students then determined that the max static friction force was equal* to gravity x the mass of the water&cup. Also, friction force equals the coefficient of friction x N.
Therefore in order to find the static friction coefficient, students plotted the graph of Normal force versus the max static friction force. Since slope is y/x, in this case it would be Normal force/ max friction force which would theoretically yield the max static friction coefficient.
The Graph:
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