Use the Inclined Plane, Pulley, String, Masses and Possibly Stopwatch To

AP PHYSICS C FRICTION LAB

OBJECTIVE – Find the coefficient of static and kinetic friction between a block and an inclined plane using hanging masses to provide the “pulling” force.

Use the inclined plane, pulley, string, masses and possibly stopwatch to: 1) find the coefficient of static friction between the block and the inclined plane. 2) find the coefficient of kinetic friction between the block and the inclined plane.

In both situations, I am asking you to use the following apparatus.

Obviously, you will want no movement when solving for static friction, but remember the inequality in the equation for static friction (). It would be best to solve for static friction when the block is on the verge of sliding, or when . When solving for kinetic friction, you will certainly have movement, you just need to decide what type of movement (constant velocity or constant acceleration). As always, do multiple trials – in this case that means different masses and different angles – 3 different trials please.

PROCEDURE – Briefly, but thoroughly detail the steps you will take to solve for each coefficient.

DATA – Neatly and logically record your data in table form. Be sure to include units.

ANALYSIS – At least one sample calculation of each must be shown explicitly (literally), then the rest of the results can be shown in table form. Be sure to include units.

CONCLUSION – Plenty of possibilities here. Think and write.

QUESTIONS (Answer these after the conclusion)

1. Take one of your trials for static friction and solve for the tension in the string. Then solve for the tension in one of your trials for kinetic friction. Show all work.

2. Take the angle and mass of the block on the incline from one of your trials for kinetic friction and determine the necessary hanging mass to allow the block to slide down or up (only choose one - which ever direction you did not use in your lab procedure) the inclined plane at a constant speed.

3. Do the values of static and kinetic coefficients of friction vary with different trials? Explain.