# Homework Help: Kinetic friction and acceleration

1. Dec 4, 2013

### pumpernickel

Hello everyone, I would appreciate some help with this problem:

The coefficient of kinetic friction between the 1.2 kg block in the figure below and the table is 0.38. What is the acceleration of the 1.2 kg block?

2. Relevant equations

F=M*A
Fk = μk * N

3. The attempt at a solution

I created freebody diagrams and came up with these

Block A: +T1 - WAE = Ma * a
Block B: + T2 - T1 - fk = Mb * a
Block C: + WCE - T2 = Mc * a

So I combined equations and came up with

WCE - WAE - fk = (Ma * a)+(Mb * a)+(Mc * a)

and fk= μk * N

and I thought it would be .38*1.2*9.8

but I know I am doing something wrong I just don't know what

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2. Dec 4, 2013

### PhanthomJay

Looks ok to me....o wait I didn't check your combined equation..stand by....

Yes, looks good! Solve for a .

Last edited: Dec 4, 2013
3. Dec 4, 2013

### pumpernickel

Alright, I redid my algebra and that is where the problem was.....I am rather embarrassed! Thank you for your help PhanthomJay.

4. Dec 4, 2013

### PhanthomJay

Great, good work, welcome to PF!