Question

Design an experiment that you could perform in our lab to determine the coefficient of kinetic friction and static friction and to compare the coefficient of kinetic friction and static friction. A good design should include details of the materials and equipment needs, the experimental procedure, including precautions, the types of data you will collect, how the data will be represented and analyzed, and how you will determine the accuracy of your experimental result(s).

Answer 1

Part 1

In this experiment, we calculate the coefficient of kinetic friction and test factors which affect friction. We pull a wooden block across a surface to determine whether the surface area of the block or the type of surface affects friction. We have to find the value of the coefficient of friction and also we can test whether the surface area of the block affects the coefficient of kinetic friction or not, and how the types of materials in contact affects to the coefficient of kinetic friction.

Part 2.

Part 3

To calculate the coefficient of kinetic friction, we need a small wooden block, that has one side covered with Teflon tape. The block has a string attached to one face. This string is threaded over a pulley, and is connected to a mass hanger. We add paperclips to the mass hanger to increase its weight until the wooden block starts to move. Addition of paperclips increases the tension in the string. This will cause the block to slide across the surface. The set up for the experiment is shown in Part 2.

So, required equipments are wooden blocks, extra masses, small and large paperclips(you can also use masses that can be attached to the string), a string, a pulley, a hanger if paperclips are used, surface on which the friction will be measured.

Part 4

List of variables you will directly measure :

Mass of the Wooden Block, Mass of the small and large paperclips or masses, Mass of the hanger, Mass of blocks added with the wooden block.

Part 5

List of variables you will calculate from these parameters :

Tension(T) in the string, Normal Force(N) on the block, Coefficient of Kinetic Friction(uk) from the Normal Force and Tension using the formula ,uk = (T/N)

We will start with no mass on the wooden block, then we add a 50 g mass to the block for each successive trial. Once the total added mass reaches 250 g, we can calculate an average of the coefficient of friction values, as shown below:

uk=(u1+u2+u3+.....+un) / n

a) To get the block to move across the surface, we add paperclips to the mass hanger until the block would just start to move. We are able to find the Tension(T) in the string using equation : T = mh*g, where mh is the total mass of hanger and the paperclips together, g is 9.81m/s2

b) We can calculate the Normal Force(N) on the block by using the formula : N = (M + m)*g, where M is mass of wooden block, m is mass of total added mass, g is 9.81m/s2

c) Now we are able to find the coefficient of kinetic friction(uk) by using the formula : uk = (T/N) , where T is tension, N is normal force.

d) Repeat steps a,b,c by adding 50 gram mass on the wooden block and increase the mass by 50 gram in successive measurements until 4 or 5 more measurements of uk.

e) Take the mean of the calculated values of coefficients of kinetic frictions.