# The Atwood machine.

1. Sep 22, 2013

### thatguy101

1. The problem statement, all variables and given/known data
Three objects with masses m1 = 35.1 kg, m2 = 16.8 kg, and m3 = 10.5 kg are hanging from ropes that are redirected over pulleys. What is the acceleration of m1? Negative numbers for downward, and positive numbers for upward, please.

2. Relevant equations
F=ma
a=(m1-m2)g/(m1+m2)

3. The attempt at a solution
So I started the problem by saying that m1*g-(T1+T2)=m2*g+m3*g (T1 connects m2 and m1, T2 connects m3 and m1)
And T1=m2*a-m2g and T2=m3*g-m3*g. and substituted in for T1 and T2. Am I heading in the right direction?

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2. Sep 22, 2013

### Andrew Mason

Your reasoning is not clear. The force on m1 is m1g minus the tensions. What is that equal to? Use that as your first equation.

Express the tensions in terms of m1, m2, g and a. You should get two equations.

That will give you three equations and three unknowns. Then you will be able to solve those equations for T1, T2 and a.

AM