Coefficient of friction and normal force

[IMSTUCK]

Homework Statement

We have a block of wood that has a weight of 95.5g lying on another flat piece of wood. The block of wood has a string attached to a tray that hangs over a pulley. Wehad to add weight to the block adn then to the tray to see how much weight in the tray would break the block free and keep it moving at a constant velocity.
We did this six times.
1.N=.94n
2.N=2.9n
3.N=4.86n
4.N=6.82n
5.N=8.78n
6.N=10.74n
N=normal force n=Newtons
On the first try we added 7g to the tray hanging vertically over the pulley and the block broke free and moved at a constant velocity so the force to keep the block moving uniformly is 7gx9.8m/s/sdivided by1000 is .069n. and so on

Homework Equations

N=mg
Fr=$$\mu$$kN

The Attempt at a Solution

I am completely lost at this point and obviously am missing something. I am not comprehending how to calculate the coefficient of friction static/kinetic with the information that I have and how they relate to normal force

 

[edgepflow]

The coefficient of static friction is a number greater than zero and less than 1. It relates the force needed to overcome friction to start moving an object and the object's weight.

It is all in your formulas - have another look.

 

[PhanthomJay]

Don't forget to add the weight of the tray. Together the weight of tray plus the weight of the mass sitting on it is equal to the tension in the string holding them, per Newton 1. Since the coef of static friction is almost always greater than the coef of kinetic friction, the first amount of weight gets the block to just move, then you have to reduce the weight to keep it moving at constant velocity. I'm not sure how you determined it was moving at constant velocity. The tension in the string pulling the block is the same as the tension in the string holding the tray if you ignore the pulley mass and and friction in the pulley (this will be a source of error). Knowing the tension allows you to calculate the coef of friction per your equation and Newton's First Law.