# Questions tagged [classical-mechanics]

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].

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### Constraint equation for an elastic pendulum

I would like to know if you can help me determine the restraining force for an elastic pendulum. The problem is the following A particle of mass $m$ is suspended by a massless spring of length $L$. ...
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### "Natural frequency" seems to be a poorly defined concept [closed]

Per wikipedia: natural frequency, also known as eigenfrequency, is the frequency at which a system tends to oscillate in the absence of any driving force. Let's take a wine glass as an example. The ...
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Reading through the "Solution as the real part of complex exponential" section of the John Taylor textbook on classical mechanics, I noticed the following : $x(t) = C_{1}e^{i\omega t} + C_{1}... 1 vote 1 answer 26 views ### Finding the tipping force for a cantilever table [closed] How would I find the force it takes to the table to tip over if you were sit on top the cantilever end? 0 votes 0 answers 49 views ### The dreaded incline plane [closed] Source: Principles of physics 11th edition halliday Chapter 6 Q11. Yes, this is a homework question and I am questioning my misconceptions. Answer at back says 3.9m/s^2 downwards. Standard inclined ... -4 votes 0 answers 43 views ### Proof that two vectors [closed] Calculate the result of this three vectors:a(vector no.1)=5u,b(vector no.2)= 7u,c(vector no.3)=4u.Calculate the resultant of the three if the angles between axis Ox and vector a is 30 degrees,the ... 1 vote 0 answers 21 views ### Energy conservation and Lorentz invariants [closed] In relativistic collision theory,How can we deduce energy is conserved by using Lorentz transformation? 1 vote 0 answers 31 views ### How do 4-vectors change under an "accelerated" Lorentz transformation? I assume that an observer moving with velocity$\mathbf{v} = v\mathbf{n} = \mathbf{v}(t)$(with respect to another observer) has coordinates where$x^{\mu}$are the coordinates for the observer who ... 0 votes 0 answers 21 views ### A question about space inversion symmetry of parity in a rotated disk In a rotated disk (say, Faraday disk), is the space inversion symmetry of parity still preserved? 0 votes 0 answers 12 views ### Reading on weighing scales at the equator of a moon in a tidally locked two-body system I'm trying a made-up extension of this problem. Consider the planet Mars and its moon Deimos, which can be approximated as meeting the following simplifying conditions: Both objects are perfect ... 2 votes 2 answers 95 views ### Help in understanding this derivation of Lagrange Equations in Non-Holonomic case Whittaker, Analytical dynamics pg 215 I don't understand how we get the final equations relating$Q_r$with$\lambda$given the conditions above? 0 votes 2 answers 59 views ### Solving forced harmonic oscillator differential equation using fourier transform I am trying to solve the equation of a forced harmonic oscillator using Fourier Transform. I know that if a function$f(t)$is such that$\lim_{x->\pm \infty} f(t) = 0$, then $$\frac{1}{\sqrt{2\pi}}... 0 votes 0 answers 18 views ### Find collision time from velocity [closed] A rock falls toward a static planet with velocity v(x) = 1/(2x) m/s where x is their separation. If initially the rock was at x = 0 and the planet at x = 1000m, when does the rock hit the planet? Hint:... 2 votes 1 answer 61 views ### Independence of generalized coordinates in the derivation of Lagrange equations from d'Alembert's Principle I am confused by this remark in the derivation of Lagrange equations from d'Alembert's principle in Goldstein: I am not comfortable that I understand why, at this late stage of the derivation, they ... 0 votes 1 answer 43 views ### Kinematics - confusion about signs of angular velocity and acceleration (general rule ?) [closed] I have often found it challenging to determine the direction of angular velocity and acceleration in exercises involving rotational motion, much like the one depicted in the picture below. While ... 0 votes 1 answer 19 views ### Getting different answers by different methods for angle made by a pendulum moving with constant acceleration A point mass m is hanging by a string of length l in a car moving with a constant acceleration a. Using car frame and pseudo force, we easily get that the angle made by string with vertical is : ... 1 vote 5 answers 159 views ### Why does \vec{r}\cdot\dot{\vec{r}}=r\dot{r}? Why is$$\vec{r}\cdot\dot{\vec{r}}=r\dot {r}$$true? Before saying anything, I have seen the proofs using spherical coordinates for$$\dot{\vec {r}}= \dot{r}\vec{u_r}+r\dot{\theta}\vec{u_\theta}+r\sin\... 0 votes 2 answers 77 views ### Question about velocities in different reference frames Suppose$\hat{x^{'}}, \hat{y^{'}}, \hat{z^{'}} $are the unit vectors of an inertial frame and$\hat{x}, \hat{y}, \hat{z} $are the unit vectors of a frame which maybe accelerating, rotating, whatever.... 0 votes 1 answer 56 views ### Doubt in fictitious forces chapter in Morin The question is this - I know 2 is what the non-inertial frame measures, but isn't$\frac{d\mathbf{A}}{dt}$the real thing, the physical thing? And you can write that too in terms of the unit vectors ... 1 vote 0 answers 24 views ### Weird sign in EOM: Centripetal vs. centrifugal term [duplicate] Something goes wrong when I was deriving the equation of motion in Kepler's probelm, as below, Angular momentum conservation$L = Mr^2\dot{\theta}^2$. And Lagrangian is$L = \frac{1}{2}M(\dot{r}^2 + ...
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Consider a free body, not hinged about any point. If a force is applied to one end of the body, the body has a net nonzero torque about many points in space. About which will it rotate? Am I wrong in ...
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### Lagrangian mechanics and generalized coordinates

In Lagrangian mechanics, we use what is called the generalized coordinates (gc's) as the variable of the machanics problem in hand. These gc's represent the degrees of freedom that the studied system ...