## How do you find the equation of motion from Hamiltonian?

14.3: Hamilton’s Equations of Motion

- L=L(qi,˙q)
- dL=∑i∂L∂qidqi+∑i∂L∂˙qid˙qi.
- dL=∑i˙pidqi+∑ipid˙qi.
- H=∑ipi˙qi−L.
- H=H(qi,pi)
- dH=∑i∂H∂qidqi+∑i∂H∂pidpi,

**What is the relation between Lagrangian and Hamiltonian?**

The Lagrangian and Hamiltonian in Classical mechanics are given by L=T−V and H=T+V respectively. Usual notation for kinetic and potential energy is used. But, in GR they are defined as L=12gμν˙xμ˙xν,H=12gμν˙xμ˙xν. The Hamiltonian above is defined to be a “Super-Hamiltonian” according to MTW.

### What is Lagrange equation of motion?

One of the best known is called Lagrange’s equations. The Lagrangian L is defined as L = T − V, where T is the kinetic energy and V the potential energy of the system in question.

**What is Hamilton’s principle function?**

Hamilton’s principle determines the trajectory q(t) as a function of time, whereas Maupertuis’ principle determines only the shape of the trajectory in the generalized coordinates.

#### What is the equation of motion using direct and Hamiltonian principle?

δS=δt2∫t1(T−U)dt=δt2∫t1Ldt=0. The integral S is called the action integral, (also known as Hamilton’s Principal Function) and the integrand T−U=L is called the Lagrangian. This equation is Hamilton’s Principle.

**Why do we use Lagrangian?**

One of the attractive aspects of Lagrangian mechanics is that it can solve systems much easier and quicker than would be by doing the way of Newtonian mechanics. In Newtonian mechanics for example, one must explicitly account for constraints. However, constraints can be bypassed in Lagrangian mechanics.

## Where is Euler Lagrange equation?

The Euler-Lagrange Equation, or Euler’s Equation Definition 2 Let Ck[a, b] denote the set of continuous functions defined on the interval a≤x≤b which have their first k-derivatives also continuous on a≤x≤b. The proof to follow requires the integrand F(x, y, y’) to be twice differentiable with respect to each argument.

**What do you mean by Hamilton principle?**

. Hamilton’s principle says that for the actual motion of the particle, J = 0 to first order in the variations q and qq . That is, the actual motion of the particle is such that small variations do not change the action.

### How do you use D Alembert’s principle?

The second law states that the force F acting on a body is equal to the product of the mass m and acceleration a of the body, or F = ma; in d’Alembert’s form, the force F plus the negative of the mass m times acceleration a of the body is equal to zero: F – ma = 0.

**Which is better Lagrangian or Hamiltonian?**

(ii) Claim: The Hamiltonian approach is superior because it leads to first-order equations of motion that are better for numerical integration, not the second-order equations of the Lagrangian approach.

#### When did Hamilton come up with the Lagrange principle?

Hamilton published two papers in 1834 and 1835, announcing a fundamental new dynamical principle that underlies both Lagrangian and Hamiltonian mechanics.

**How are the Lagrange equations of motion generated?**

These last equations are called the Lagrange equations of motion. Note that in order to generate these equations of motion, we do not need to know the forces. Information about the forces is included in the details of the kinetic and potential energy of the system. Consider the example of a plane pendulum.

## How did Hamilton derive the principle of least action?

Hamilton was the first to use the principle of least action to derive Lagrange’s equations in the present form. He built up the least action formalism directly from Fermat’s principle, considered in a medium where the velocity of light varies with position and with direction of the ray.

**How to rephrase Hamilton’s principle based on generalized coordinates?**

Based on the introduction of the Lagrangian and generalized coordinates, we can rephrase Hamilton’s principle in the following way: