this is a system of three masses attached to a string, hanging on two fixed pulleys.(adsbygoogle = window.adsbygoogle || []).push({});

I want to find the equation of motion of the middle mass, given the initial condition P(0)=X

Assuming all friction, stretching of the strings, and momentum of the pulleys are negligible.

The string has a fixed length overall, the length of string between masses is equal, and the masses are also equal.

I get confused because I'm trying to keep track of too many variables, there are 4 angles, 3 tensions, 3 positions... I know there's a better way to do this, any help would be appreciated.

here's a diagram I made... thanks for any help!

[PLAIN]http://img828.imageshack.us/img828/1610/3mass2pulleysystem.jpg [Broken]

**Physics Forums | Science Articles, Homework Help, Discussion**

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Mechanics, 3 coupled masses. don't worry, no springs!

**Physics Forums | Science Articles, Homework Help, Discussion**