How Does Friction Affect Heat Generation in a Mechanical Work Experiment?

[joshmo259]

We are doing a lab now to prove the connection between heat and work.
the experiment consists of a a cylinder that is rapped with a nylon string which in turn suspends a bucket of mass m.
by turning the cylinder we create a frictional force that creates heat ( the heat is then measured)

my question regards how we calculate the work done. the equation we were given was

mg2pir

the reason is since the work=fd, the force being applied is the mass of the bucket and the distance is the circumference of the cylinder

my question is why don't we need also need to know the coefficient of kinetic friction between the cylinder and the string. if we were to tie a rubber string around the cylinder wouldn't it create more friction and hence more heat. why is the friction simply calculate as mg?

thanx

 

[jbsteele]

in advance The coefficient of kinetic friction is not necessary to calculate the work done in this experiment. The work done is simply the product of the force applied and the distance moved in the same direction. Since the force applied is the mass of the bucket, and the distance moved is the circumference of the cylinder, the equation you were given (mg2pir) is correct. The coefficient of kinetic friction does not need to be included because it does not affect the amount of work done, only the amount of heat generated as a result of the friction.