Clasccal mechanics Definition and 15 Threads

  1. inuka00123

    High School Question about Newton's 3rd law: Two boxes sliding toward each other and colliding

    imagine a person pushing a 10Kg cardboard box with 20N of force toward a 5Kg cardboard box, with the second law we can calculate it is moving at 2ms/s acceleration toward the 5Kg box, relative to the 10Kg box we can say the 5Kg box is moving toward the 10Kg box with 2ms/s acceleration with a 10N...
  2. tragtf

    Unit vectors that change as a function of time

    we can express theta as a product of the angular velocity and time thus plugging this in space of theta in the above equations we can express r hat and theta hat as a function of time. But i am having problems in integrating them and again converting them back to the terms of r hat and theta hat...
  3. G

    Undergrad Noether’s theorem -- Question about symmetry coordinate transformation

    Let's say we got one particle in x direction only and we got some motion x(t) which we figured it out through Lagrangian. In Noether's theorem for coordinate transformation symmetry, we start with the following: x(t)' = x(t) +εf(t) (ε - some number) - I denoted new path with x(t)' I'm...
  4. brochesspro

    Undergrad Meaning of the terms in the formula of the net external force

    The mathematical representation of the net external force on a system(obtained from Newton's second law) is ##\vec F_{net} = \frac {d\vec P}{dt}##, which is the rate of change of linear momentum of the system. If we substitute ##\vec P = m\vec v## into the formula for force and differentiate, we...
  5. gromit

    Using Lagrangian to show a particle has a circular orbit

    Hi :) This is a problem from David Tong's Classical Dynamics course, found here: http://www.damtp.cam.ac.uk/user/tong/dynamics.html. In particular it is problem 6ii in the first problem sheet. Firstly we can see the lagrangian is ##L = \frac{1}{2}m(\dot{r}^2+r^2\dot{\theta}^2+\dot{z}^2) -...
  6. D

    Finding the period of an orbit ##r=a(1+\cos\theta)##

    I've already found the potential and force that produce the given orbit. my results were: ##V=-\frac{al^2}{mr^3}## ##\vec{F}=-\frac{-3al^2}{mr^4}\hat{r}## Now, I've been trying to find the period using the equation ##t=\sqrt{\frac{m}{2}}\int_{r_0}^{r}\frac{dr'}{\sqrt{E-V_{eff}}}## Using...
  7. S

    Undergrad Classical mechanics -- Equations for simulating the motion of a body

    Hello forum, i want to make a samulation of a body. The body will be moved horisontal on y,x axis. I want on my simulation the body to change direction many times(for example i want to go for 10sec right and then left end right...). My question is does i need more than one differential equation...
  8. V

    Classical Textbook for light, heat, waves

    There's an undergraduate physics course at my uni that covers these topics and the course description is: Mathematical descriptions for classical physics: oscillations, mechanical waves, electromagnetic waves, physical optics and thermodynamics. Are there any good studying materials/textbooks I...
  9. A

    Undergrad Galilean Invariance and constraints on Forces.

    Let's say we have a system of two point particles that can interact with each other by forces that are position and velocity dependent. The forces might or might not be derivable from a generalized potential. Assuming Isotropy of space and homogeneity of space and time, what are the constraints...
  10. G

    Graduate Conservation of angular momentum in scattering processes

    Greetings. So... let us consider a particle moving in the yz plane, coming from the infinite towards a region were a gravitational potential is appreciable. The Lagrangian of the system is \mathcal{L} = \frac{1}{2}\mu (\dot{r}^2+r^2{\dot \phi}^2) + \frac{G\,m\,M}{r} where \mu is the reduced...
  11. Manolisjam

    Prove the average external force is Zero

    1.Problem statement Prove the average external force of a system of particles N starting from rest and ending at rest is zero.Homework Equations If the system moves periodically prove the av. external force is zero in a period The Attempt at a Solution I don't quite understand what i am asked...
  12. J

    Undergrad Lever, bar, and mechanics why does this happen?

    two saipens one known as Alpha who is on the left and the other on right Beta are present, Alpha first presses down on a bar and Beta has to use all of its strength to lift Alpha's hand a distance h a distance, in this scenario the fulcrum is placed close to Beta, now in the next scenario it is...
  13. T

    High School Why it's easier to push the door from the furthest distance

    Why it's easier to push the door from the furthest distance From the pivot point?
  14. M

    Undergrad Solar system simulation errors

    Hi, as a side project I am making a solar system simulator in Python, but I am getting extreme inaccuracies. As the image shows - I am comparing the simulation to data obtained from NASA's Horizon. I have written a a basic Verlet integrator in the Python class posten below: import numpy as...
  15. LouysHong

    Undergrad Launching a particle at the highest point inside a sphere

    If a smooth sphere with radius a is fixed on a plane, and a particle is projected horizontally at the highest point outside/on of the sphere with speed (4ag/5)^0.5, I know that the particle will lose contact with the sphere when it makes an angle of theta with the upward vertical, where theta is...