Question

You are given two blocks of wood and asked to measure the coefficient of kinetic friction between them. Design an experiment to make this measurement. Your design may involve any equipment that is typically available to you in the lab (masses, rulers, springs, etc.). Write a detailed plan of your experiment. Your plan should include:

1. A description of the design of the proposed experiment with a sketch.

2. A list of all equipment you will need for the experiment.

3. A list of all variables you will directly measure.

4. A clear mathematical model that allows you to calculate the desired number from the quantities you measure directly.

Answer 1

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.

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