- #1

curiousPep

- 17

- 1

Imagine I throw a pencil. For that I have 5 generalised coordinates (x,y,z and 2 rotational).

When I express Kinetic Energy (T) as:

$$T = 1/2m\dot{x^{2}}+1/2m\dot{y^{2}}+1/2m\dot{z^{2}} + I\dot{\theta^{2}} + I\dot{\phi^{2}}$$

and potential energy (V)

$$V=mgz$$

Then I use Lagrangian to find the EOM.

For x,y,z is fine but for $$\theta$$ and $$\phi$$ I have a question. I see how x,y,z can be a expressed as functions of $$\theta\;and\;\phi$$, but why should I do this. I mean in cases that something is less obvious, then I will get the wrong EOM.

Thank you, and I hope the latex code works.