# Homework Help: Pulley system

1. Nov 26, 2008

### devanlevin

2 masses are tied in the followin configuaration, the 1st with a mass of m1 the 2nd mass of m2, pulleys and ropes have no mass or friction.

what is the acceleration of each mass, using only parameters g, m1, and m2

not too much i can see from this, i know that |a1|=2|a2|,
i think that
1 F=m1a=m1g-T
a1=g-T/m1

2 F=m2a=m2g-2T
a2=g-2t/m2

Last edited by a moderator: May 3, 2017
2. Nov 26, 2008

### ak1948

looks right to me.

3. Nov 26, 2008

### Staff: Mentor

So far, so good. But now you need to combine all three equations to solve for a1 & a2 in terms of the given parameters. Hint: Careful with signs. If a1 is down, a2 must be up.

4. Nov 26, 2008

### devanlevin

a1=-2*a2,

a1=g-T/m1

a2=g-2t/m2
-------------------
T=m1(g-a1)=m1(g+2a2)

a2=g-[2m1(g+2a2)]/m2
m2a2=g-(2m1g)-(4m1a2)

a2(m2+4*m1)=g(1-2*m1)

a2=g*(1-2m1)/(m2+4m1)

is that correct,?? the answer in my textbook is similar, either a mistake on their behalf or im missing something,, their answer is

a2=g*(m2-2m1)/(m2+4m1)

5. Nov 26, 2008

### Staff: Mentor

You made an error in this step. Note how the terms in your last equation all have the same units--except one. (When you multiplied by m2, you did not do it completely.)

6. Nov 26, 2008

thanks