# Atwood Question

1. Jul 16, 2006

### Tensaiga

i drew a digram for the forces and i found out the equations for accerleration... then i'm stuck...

Question: Determine the tension in the strings, the acceleration, and how far the masses will go in 2.0s. (See attachement)

Well i drew a FBD, ,and i got three eqations for accerleration:
for mass 1 (100g):
A = (T2 - M1*G)/(M1)
A = (T2 - 0.1*9.8)/(0.1)

mass 2: (200g, on the floor)
A = (T1 - T2)/(M2)
A = (T1 - T2)/(0.2)

mass 3: (200g, going down on the right)
A = (M3*G - T1)/(M3)
A = (0.2*9.8 - T1)/(0.2)

Then what should i do after this? i can't equate 3 equations at once... can i?

#### Attached Files:

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2. Jul 16, 2006

### Andrew Mason

Why not? After all, if the string does not break the accelerations are all the same. Try inserting the expressions for T1 and T2 from equations 1 and 3 into 2. That will give you an equation with only one unknown: A.

AM

3. Jul 17, 2006

### Tensaiga

yea i tried that, but a strange number came out... i will try again, maybe it's a algebra error.

4. Jul 17, 2006

### nrqed

Your equations look right. Did you solve for both tensions and for the acceleration? If so, there is an easu way to tell if you made an algebra mistake: just plug back your values in the initial equations! If it does not work, it shows that you made an algebra mistake.

Patrick