# Homework Help: Mobile of Fish in equilibrium

1. Apr 16, 2010

### Isimanica

1. The problem statement, all variables and given/known data
The mobile is in equilibrium. The fish B weighs
27 oz. Determine the weights of fish A, C and D.
(The weights of the crossbars are negligible).

2. Relevant equations
Moment = Force*Distance

3. The attempt at a solution
My idea here is to use the moments about each point, solve for one variable. Here is what I have com up with so far, am I on the right track?
D(14)=A(4) since their moments at that point are in equilibrium.
B(4)=12(A+D)
C(24)=6(A+B+D)
Am I wrong in setting it up this way?

2. Apr 16, 2010

### Staff: Mentor

So far so good.

3. Apr 16, 2010

### Isimanica

So then I just say that I set A=D(14)/4
Replace A in equation B(4)=12(D+ (D(14)/4))
Solve for D and then replace D and A values that I get into the equation for
C(24)=6(B+D+A) solve for C and that is it??? Please tell me that it wasn't that simple?

4. Apr 16, 2010

### Staff: Mentor

As you wish.

It wasn't that simple :tongue2: