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

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Discussion Overview

The discussion revolves around simulating the motion of a body moving horizontally on the x and y axes, particularly focusing on how to model changes in direction using differential equations or other methods. The scope includes theoretical aspects of motion, mathematical modeling, and practical implementation in simulations.

Discussion Character

  • Exploratory
  • Technical explanation
  • Homework-related
  • Mathematical reasoning

Main Points Raised

  • One participant questions whether multiple differential equations are necessary to describe the motion of a body that changes direction multiple times.
  • Another participant suggests that a simple prescription for motion might suffice, questioning the need for differential equations.
  • A participant describes a dynamic model involving an instantaneous force to move the object right and a counterforce to move it left, expressing uncertainty about the appropriateness of this method.
  • A participant inquires about the background of the original poster, specifically their familiarity with Newton's Laws of Motion and Free Body Diagrams (FBDs).
  • The original poster shares their background in mechanical engineering and their goal of simulating an inverted pendulum, indicating a desire to understand how to mathematically describe the change of force that causes direction changes.
  • One participant suggests using kinematic equations for constant acceleration with stepwise continuous vector forces as a simpler starting point for the simulation.
  • A participant seeks clarification on the representation of Newtons and unit vectors in a provided force profile example.
  • Another participant explains that N represents Newtons, the SI unit of force, and that \(\hat x\) denotes a unit vector in the x-direction.

Areas of Agreement / Disagreement

Participants express varying opinions on the necessity of differential equations versus simpler models for simulating motion. There is no consensus on the best approach to model the changes in direction or the forces involved.

Contextual Notes

Participants discuss the potential complexity of modeling forces and direction changes, highlighting the need for clarity on the mathematical representation of these concepts. There are unresolved questions about the specifics of the simulation approach and the underlying physics.

Who May Find This Useful

This discussion may be useful for students and practitioners in mechanical engineering, physics, and computer simulations, particularly those interested in motion dynamics and control systems.

s1mos_tsr
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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 to describe this type of motion?
thanks in advance lovers of physics
 
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Hello @s1mos_tsr , :welcome: !

What causes the body to move/change direction ?
As a minimum you don't need a differential equation at all, just a prescription for the motion...
 
Lets say that the object has a inside mechanins to produce force, for example at t=0 a instand force make the object to move right and at t=10 a counterforce make the object to move left. In my mind i have a plan to make a dynamic model to have the simulation i don't know if this is the right method.
 
s1mos_tsr said:
Lets say that the object has a inside mechanins to produce force, for example at t=0 a instand force make the object to move right and at t=10 a counterforce make the object to move left. In my mind i have a plan to make a dynamic model to have the simulation i don't know if this is the right method.
Welcome to the PF. :smile:

Can you say a bit about your background so far in math and physics? Are you familiar with Newton's Laws of Motion?

https://en.wikipedia.org/wiki/Newton's_laws_of_motion

Are you familiar with drawing a Free Body Diagram (FBD) of an object to help in calculating the motion resulting from forces and torques ("moments") applied to the body?
 
I am studying mechanical engineering and i started a project about control systems. My project is to make a simulation on MATLAB of an inverted pendulum but because its a little bit deep for me i wanted to start a easier simulation on MATLAB like a free fall body and moving body on surface. My goal is to achieve the control the pendulum. I want also to make it more visual and try to animate the simulation. I have good background on statics systems but on the dynamics models i am not so good. My main question this moment what i said at the 1st post and also how to describe with maths the change of force that makes the body to change direction.
** at t=0 a instand force make the object to move right and at t=10 a counterforce make the object to move left
 
Last edited:
Well, if you use stepwise continuous vector forces, you can use the kinematic equations of motion for constant acceleration, which simplifies things a lot, right? Maybe start with that, and then later move on to discrete simulations of motion where the forces vary with time.

What would the motion of a 1kg mass be like given this piecewise continuous force profile?

##0s < t \leq 1s : F = 1N \hat x##
##1s < t \leq 2s : F = 3N \hat y##
## 2s < t \leq 3s : F = -2N \hat x##
 
Ok i think i get it a little bit. The point is to change the force(by changing the the sign) while the code is running at the time you want, correct me if i am wrong. But on the image i don't understand what N and X(hat) represents there.
 
##N## is Newton, SI unit of force (kg m/s2)
##\hat x## is a unit vector in the ##x##-direction
 

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