# Explanation of a Foucault pendulum

The equations of motion of a Foucault pendulum is given by:

$$\ddot{x} = 2\omega \sin\lambda \dot{y} - \frac{g}{L}x$$ $$\ddot{y} = -2\omega \sin\lambda \dot{x} - \frac{g}{L}y$$

where $\omega$ is the rotational frequency of the earth which has a value of $7.27 x 10^-5$, $\lambda$ is the latitude of where the pendulum is, $g$ is the acceleration due to gravity, $L$ is the length of the pendulum's string. What I don't know is what does $x$ and $y$ represent? I have read some derivations of these equations but I really cant figure out what they are trying to say.

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Possible duplicate: physics.stackexchange.com/q/55650/2451 –  Qmechanic Mar 9 '13 at 8:00

The $x$ represents the x-coordinate of the pendulum.
The $y$ represents the y-coordinate of the pendulum.
$x$ and $y$ are perpindicular to each other, but parallel to the Earth's surface. $z$, not mentioned in these equations is height.