# Force of Friction w/o Coefficient of Friction Given

1. Feb 4, 2012

### stehat

I am having trouble determining what the force of friction of the box on a table described as below:

Two blocks are arranged at the ends of a massless string. M1 is on the table. M2 is attached to another side of the rope hanging off of the side of a table with a massless pulley (90 degrees from the table).

M1= 4.78KG
M2 = 3.26 KG

When M2 has fallen through .396m, its downward speed is 1.29 m/s. Acceleration of gravity is 9.8. What is the frictional force between M1 and the table?

My first step was to find the acceleration with I figured to be 4.202. (By taking the acceleration formula A=V2-V1/T2-T1. I figured the time in this formula by using the velocity formula and solved for T.

My next step was to figure out the tension force which I think is where I am getting confused on where to go. I want to find the Tension force and subtract that from the Net force to find the force of friction, but I am having difficulty determining the net force an now I am not so sure I am figuring out the tension force correctly.

2. Feb 4, 2012

### tiny-tim

welcome to pf!

hi stehat! welcome to pf!

(btw, always use a small "t" for time, so as not to confuse with tension )
i don't follow this: what formula did you use?
yes, M2a = M2g - T …

now do a similar F = Ma equation for the other block