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Classical mechanics discusses the behaviour of macroscopic bodies under the influence of forces (without necessarily specifying the origin of these forces). If it's possible, USE MORE SPECIFIC TAGS like [newtonian-mechanics], [lagrangian-formalism], and [hamiltonian-formalism].

3 votes
2 answers
1k views

Non-Holonomic constraints

I am struggling to understand how to determine whether the constraints are nonholonomic. For an example: "Consider a disk which rolls without slipping across the horizontal plane, what is the best ge …
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3 votes
0 answers
88 views

Help with Newton's 3rd law

I am using the book Classical Dynamics of Particles and Systems by STEPHEN T. THORNTON, JERRY B. MARION and they say that Newton's 3rd law only applies when forces are $\textbf{central forces}$, basic …
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  • 283
3 votes
2 answers
76 views

Perturbation Method: What is the acceptable method to terminate expansion

I am using the book Classical Dynamics of Particles and Systems by STEPHEN T. THORNTON, JERRY B. MARION, page: 67 and they use perturbation method to approximate: \begin{equation} T = \frac{kV + g}{g …
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1 vote
0 answers
41 views

Using normal displacement instead of virtual displacement

I know that there are many posts about virtual displacement, but I want to answer the question if of: is virtual displacement is always needed to get the same results? I am going through a PDF by Subh …
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  • 283
0 votes
2 answers
81 views

Help with deriving the Euler-Lagrange equation (evaluating at $ \varepsilon = 0$ before solv...

I am using wiki here to help me understand the deriving of the euler-lagrage equations How do we get from: \begin{equation} \left.\frac{dJ_\varepsilon}{d\varepsilon}\right|_{\varepsilon = 0} = \int_a^ …
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0 votes
0 answers
25 views

Help with deriving euler-lagrange equation (evaluating at $ \varepsilon = 0$ before solving ... [duplicate]

I am using wiki here to help me understand the deriving of the euler-lagrage equations How do we get from: \begin{equation} \left.\frac{dJ_\varepsilon}{d\varepsilon}\right|_{\varepsilon = 0} = \int_a^ …
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  • 283
0 votes
1 answer
87 views

Help with understanding virtual displacement in Lagrangian

I know that these screen shots are not nice but I have a simple question buried in a lot of information My question Why can't we just repeat what they did with equation (7.132) to equation (7.140) wit …
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Accepted

Help with understanding virtual displacement in Lagrangian

Before answering the 2 questions I would like to provide some background. Notes As the Lagrangian is the function $L(x_i,\dot{x}_i)$, which is the function of 2 variables $x_i,\dot{x}_i$. Thus the par …
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  • 283
0 votes
1 answer
21 views

Generalized forces for virtual work - Why did they drop the summation?

I am going through a PDF by Subhankar Ray & J. Shamanna on virtual work here and according to the PDF, equation 29, they write gerneralized force as: $$Q_j = -\nabla_k\tilde{V}\cdot\left(\frac{\part …
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  • 283
0 votes

Non-integrable differential equation and non-holonomic contraints

In classical mechanics, holonomic constraints are relations between the position variables (and possibly time) that can be expressed in the following form: $g(y,t) = 0$ Nonholonomic constraints is whe …
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  • 283
0 votes
1 answer
100 views

For virtual displacement in the Lagrangian, why is $\delta \dot{x_i} = \delta \frac{dx_i}{dt...

I am having trouble understanding why $$\delta \dot{x_i} = \delta \frac{dx_i}{dt} = \frac{d}{dt}\delta x_i \equiv 0.\tag{7.132}$$ you can see my explanation leading up to it below. I would greatly app …
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  • 283
0 votes
0 answers
108 views

Question on non-holonomic constraints (This is different to the others)

I know there are many posts on non-holonomic constraints and also many on this exact one but I feel that there is still some confusion on it. "Consider a disk which rolls without slipping across the …
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