Problem with learning how to use equations of motion

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Discussion Overview

The discussion revolves around the challenges faced by a newcomer to physics in understanding and applying the equations of motion. The focus is on problem setup, equation selection, and strategies for improvement in a calculus-based physics context.

Discussion Character

  • Homework-related, Conceptual clarification, Exploratory

Main Points Raised

  • One participant expresses difficulty in setting up problems and selecting the appropriate equations of motion, seeking suggestions for improvement.
  • Another participant suggests using any relevant equations and counting the number of unknowns and equations to find a solution, emphasizing the importance of practice.
  • A different participant recommends the specific equation Vfx^2 = Vix^2 + 2ax(xf-xi) as useful when time is not provided in the problem.
  • One participant offers to provide more help if specific examples of confusion are shared.

Areas of Agreement / Disagreement

Participants generally agree on the need for practice and exploration of different equations, but no consensus exists on a singular approach to overcoming the initial difficulties faced by the newcomer.

Contextual Notes

Participants mention various strategies such as dimensional analysis and the importance of physical intuition, but these methods are not universally accepted or detailed, leaving some assumptions and steps unresolved.

Who May Find This Useful

This discussion may be useful for students new to physics, particularly those struggling with the application of equations of motion in a calculus-based context.

StingerManB
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Here is my problem: I am new to physics all together, NEVER a physics course at all. I am in a Calculus Based physics class, placed there due to the A's I made last semester in calculus (and for other scheduling conflicts)
The problems involving the equations of motion are giving me trouble. Setting up the problems and which equation to use is my biggest problem.
I am just looking for suggestions to help me improve. I have tried to just do more problems, but I get stuck right at the beginning.

Any help at all or suggestions for me?
 
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Use every equation that comes to your mind, as long as you know it's right (ie. guess). Count the number of unknowns you have, and count the number of equations. When you have enough equations, solve for the unknowns.

Sometimes it helps to write the same equation in different forms, eg. F=ma=m(dv/dt)=m(d2x/dt2)

A second way is to use dimensional analysis. Look at the dimensions (length, mass, time, etc.) of the unknown, look at the knowns. Put the knowns together in some combination so that their combined dimensions will match the dimensions of the unknown. This will at least give you the form of the equation. This is dangerous, because the answer is not unique - eg. m1/m2 has no dimensions so it can enter in any combination without changing the dimensions of your equation - so you must justify the exact equation properly after using this to guess its form.

As for physical intuition about which equation to use first - practice makes perfect.
 
Last edited:
Remember to use the equation Vfx^2 = Vix^2 + 2ax(xf-xi) Helpful when you're not given the time.
 
Also, if you give me some specific examples of what you don't understand, I can help you more.
 

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