Hamilton's equations of motion

In summary, the conversation discusses finding Hamilton's equations of motion for a generic form of Hamiltonian, which includes kinetic and potential energies. The potential energy is represented by a general quadratic potential with a symmetric 3-by-3 matrix. The participants are unsure of where to begin and seek help in understanding the problem and its solution.
  • #1
physics-?
2
0
Having a bit of trouble with this question, if anyone could help?

For the following questions we assume the Hamiltonian to
be of the generic form
H(r, p) = T(p) + V (r) = p2/2m+ V(r)
where T(p) and V (r) denote kinetic and potential energies, respectively.
Find Hamilton's equations of motion for a general quadratic potential V (r) = [(r,Ar)]/2
A = AT , a symmetric 3-by-3 matrix.
Which force do you obtain?
Is this force conservative?

Thanks!
 
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  • #2
welcome to pf!

hi physics-?! welcome to pf! :wink:

show us what you've tried, and where you're stuck, and then we'll know how to help! :smile:
 
  • #3
Well if I'm honest I don't really know where to begin!
I am having trouble understanding it.
Sorry that's not much use to you!
 
  • #4
if A was diagonal, (r,Ar) would be ax2 + by2 + cz2

the off-diagonal elements add some xy and yz and zx to that
 
  • #5


Hamilton's equations of motion are a set of equations that describe the evolution of a physical system over time. They are derived from Hamilton's principle, which states that the action of a system is minimized along the path that the system takes.

In this case, we are given a Hamiltonian of the form H(r,p) = T(p) + V(r), where T(p) is the kinetic energy and V(r) is the potential energy. We are also given a specific quadratic potential V(r) = [(r,Ar)]/2, where A is a symmetric 3-by-3 matrix.

To find Hamilton's equations of motion, we first need to calculate the conjugate momenta, defined as p = ∂L/∂r, where L is the Lagrangian of the system. In this case, the Lagrangian is L = T(p) - V(r). Therefore, the conjugate momenta are given by p = ∂T/∂p = p/m and p = -∂V/∂r = Ar.

Next, we can use the Hamiltonian equations of motion, which state:

dr/dt = ∂H/∂p = p/m
dp/dt = -∂H/∂r = -∂T/∂r + ∂V/∂r = -∂V/∂r = -Ar

These equations describe the motion of the system over time, with the first equation giving the velocity and the second equation giving the acceleration. We can see that the force obtained from these equations is -Ar, which is a conservative force since it can be derived from a potential energy function.

In conclusion, Hamilton's equations of motion for this system are given by dr/dt = p/m and dp/dt = -Ar, with a conservative force of -Ar. These equations can be used to study the behavior of the system and predict its motion over time.
 

1. What are Hamilton's equations of motion?

Hamilton's equations of motion are a set of equations that describe the evolution of a physical system over time. They are derived from Hamilton's principle, which states that a system will follow a path that minimizes the action, a quantity that combines the kinetic and potential energies of the system.

2. What is the significance of Hamilton's equations of motion?

Hamilton's equations of motion are significant because they provide a powerful mathematical framework for understanding and predicting the behavior of physical systems. They are widely used in fields such as classical mechanics, quantum mechanics, and control theory.

3. How do Hamilton's equations of motion differ from Newton's laws of motion?

While Newton's laws of motion describe the relationships between a system's position, velocity, and acceleration, Hamilton's equations of motion involve the system's position, momentum, and energy. Hamilton's equations also take into account the system's potential energy, while Newton's laws do not.

4. Can Hamilton's equations of motion be applied to any physical system?

Yes, Hamilton's equations of motion can be applied to any physical system, as long as the system can be described by a set of generalized coordinates and their corresponding momenta. This includes both classical and quantum systems.

5. What is the advantage of using Hamilton's equations of motion over other methods?

One advantage of using Hamilton's equations of motion is that they provide a concise and elegant way to describe the dynamics of a system. They also allow for the use of powerful mathematical techniques, such as variational methods, to solve complex problems. Additionally, Hamilton's equations can be easily generalized to higher dimensions and more complex systems.

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