# Differential equation for unbalanced rotating force

1. Dec 9, 2014

### Dustinsfl

1. The problem statement, all variables and given/known data
$M\ddot{y} + k_{eq}y = me\omega^2\sin(\omega t)$

What is $m$?

2. Relevant equations

3. The attempt at a solution
In the ODE above, $M$ is the total mass of the problem, correct? For instance, if we had a cantilever beam, $M = m_b + m_m(0.23)$ where $m_b$ is the mass of the beam and $m_m$ is the mass of the motor.

Is $m$ the mass of the motor causing the unbalance or is it the mass of the whole system as well?

2. Dec 12, 2014

### OldEngr63

Is there no figure associated with this problem?

To just start with the ODE given, I think that the only truly correct answer is to say that
m is the 13th letter of the alphabet.

The problem is that there are many physical systems that give rise to a particular describing differential equation. To start with the ODE and ask what the parameters are is pure nonsense.