# Two pulleys system (please check my work)

1. Oct 14, 2008

### fishingspree2

1. The problem statement, all variables and given/known data
Find the acceleration of the system
http://img266.imageshack.us/img266/4904/2pulleyszw9.jpg [Broken]
The rope is massless
The mobile pulley is not massless, it weighs 20 grams.
Find the accelereation of the system

2. Relevant equations
F=mg
F=ma
g = 9.8

3. The attempt at a solution

for W1:
Fy = 2T-W1 = ma
2T-(500+20)*g = (500+20)*a
2T-520g = 520a (equation 1)

for W2:
Fy = W2-T=ma
300g-T=300a
T = 300(g-a) (equation 2)

equation 2 in equation 1 gives
a = 1,43

Is it correct?

Last edited by a moderator: May 3, 2017
2. Oct 14, 2008

### fishingspree2

i don't think it's correct.. i think there is an error in the tensions, but i don't see

Last edited: Oct 14, 2008
3. Oct 16, 2008

### fishingspree2

can someone help me?
I really want to know how to do this =(

4. Oct 16, 2008

### nasu

The equations seem to be OK. The solution is not. Try to solve again the two equations.
If you show how you solve them I can try to find the mistake, if any.
Be careful with the units. If you want to get the tension in newtons, the mass should be in kg.