Kinetic Friction Experiment Conservation of Energy Question

[elliott87]

I am currently working on an experiment to find the kinetic friction in a driveline. The experiment uses the principle of conservation of energy and is based on the following experiment: http://hyperphysics.phy-astr.gsu.edu/HBASE/Class/PhSciLab/frictionex.html

The difference in my proposed experiment is that instead of having the sliding block on the table, there would basically only be the pulley and a line would be wrapped completely around the pulley attached to a weighted system.

The initial energy balance would still be the potential energy of the hanging mass, and a withdrawal from the system would be the mass hitting the floor and losing kinetic energy. In the experiment in the link, the rest of the energy is said to go to the sliding block (assuming a frictionless pulley I'm guessing). My question is can the same methodology be used to calculate the friction in the pulley in the case of my experiment (no sliding block)? ie. Would the rest of the energy in the system, assuming it is kinetic friction keeping the mass from free falling at g, be equal to some frictional force over some distance?

 

[bucher]

If the friction is accounted for by the pulley and not the block then yes, you would be correct. The force over some distance would be the resistive force on the pulley and the distance would be the number of rotations the resistive force was exerted.

 

[elliott87]

I'm a little confused near the end of this experiment when they solve for the force exerted on the block by the string (the pulling force) to be 0.63 N and then they say the frictional force is 0.63 N as well. What is the reasoning behind this? Here is the link again: http://hyperphysics.phy-astr.gsu.edu...rictionex.html