Homework Help: How do I find the equation of motion for this object?

Tags:
1. Oct 16, 2016

1v1Dota2RightMeow

1. The problem statement, all variables and given/known data
Find the equation of motion of the object by setting the derivative of the total energy equal to zero.

2. Relevant equations
r(theta)=(Rcos(theta), Rsin(theta), q*theta)

v(theta)=dr/dt=(-Rsin(theta)dtheta/dt, Rcos(theta)dtheta/dt, q*dtheta/dt)

derivative of Total Energy = m(dtheta/dt)(d^2theta/dt^2)(R^2+q^2)+m*g*q*dtheta/dt

3. The attempt at a solution
I worked it all out to the point of finding the derivative of the total energy above. But I'm confused now. What does it mean to find an equation of motion? Let's start with that because if I don't know what an equation of motion will even look like, then I won't have any clue if I've found it or if I'm even on the right track.

2. Oct 16, 2016

vela

Staff Emeritus
3. Oct 16, 2016

kuruman

See here https://en.wikipedia.org/wiki/Equations_of_motion about equations of motion.
Other than that, please provide the complete problem statement, not just the question of what you are required to find. Also, it would be nice to use LaTeX for your equations. The time you invest learning it is worth it.