# Homework Help: Need help with Pistons

1. Apr 10, 2010

### yang09

1. The problem statement, all variables and given/known data

Piston 1 in the figure has a diameter of 0.27 in and is attached to a lever arm a distance 1.8 in from the pivot point. Piston 2 has a diameter of 1.3 in. An external force F acts on the
lever arm at a distance 20 in from piston 1 as shown below. In the absence of friction, find the force F necessary to support the 464 lb weight. Assume the height difference between the pistons is negligible.

2. Relevant equations

Force
in/Areain = Forceout/Areaout

3. The attempt at a solution

The picture is #1 on the attached files.
I'm not even sure you're supposed to use this formula, but I have no clue how to solve it. Can someone please guide me in the right direction. Thanks

1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

#### Attached Files:

• ###### problem_pdf.pdf
File size:
29.9 KB
Views:
163
2. Apr 11, 2011

### shireoki

hi, I was trying to solve the problem with the bernoulli's equation on your other post, and saw that you said you need help with this one, and i happened to just solved it, so i thought i'll stop by, hope it's not too late for your quest thing...

I did (A1/A2)*464lb
so, [pi*(0.27/2)^2]/[pi*(1.3/2)^2] times 464lb = x

then you have to do the mechanical ratio thing.. sooo

(shorter distance/ (shorter distance + longer distance) ) times the above answer you just found = what you need

[1.8/ (1.8+20)]*x = what you need

and i'm still having problem with the bernoulli's equa :(

3. Apr 11, 2011

### shireoki

and here's all the technical stuff:

x i mentioned above is force of small piston produced... fyi

technical stuff on the 2nd step:
+F1d1 - Fd = 0
+F1d1 = Fd
so F = (d1/d)*F1

4. Apr 11, 2011

### shireoki

and nvm i got the bernoulli's equ :)