How to find trajectory as a function of time with energy

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Homework Help Overview

The discussion revolves around finding the trajectory of an object under the influence of an attractive force that varies with distance, specifically F=-A/x^2. Participants are tasked with determining the potential energy and subsequently the trajectory as a function of time, given initial conditions that result in zero total energy.

Discussion Character

  • Exploratory, Assumption checking, Conceptual clarification

Approaches and Questions Raised

  • Participants discuss the relationship between force, acceleration, and potential energy, with one attempting to derive the trajectory from acceleration. Questions arise regarding the validity of using gravitational potential energy in this context and the implications of the logarithmic relationship in the position equation.

Discussion Status

The discussion is ongoing, with participants exploring different interpretations of the problem. Some guidance is offered regarding the calculation of potential energy based on force, but there is no consensus on the trajectory derivation or the correct approach to take.

Contextual Notes

Participants note that the problem setup does not conform to typical gravitational scenarios, which may affect the assumptions made about potential energy. There is also mention of the challenge in converting acceleration as a function of distance to a function of time.

Cocoleia
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Homework Statement


I am given that an object of mass m has an attractive force F=-A/x^2 acting on it, where A is a constant and x>0. I need to find the potential energy. After i need to suppose initial conditions (x0, v0) such that total energy=0. I need to find the trajectory x(t) with v>0

Homework Equations


Potential energy = mgh

The Attempt at a Solution


So far I said that F=ma and then found the acceleration. I integrated the acceleration to find the speed, then I integrated that to find the position, which is A/m ln(x). I said that the potential energy = gAln(x). From this point I am stuck, I can't figure out how to find the trajectory as a function of time.
 
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F=ma gives you the acceleration as function of distance. Converting this to acceleration as function of time (what you need for the integration steps) is not trivial.
Cocoleia said:
Potential energy = mgh
That does not work. This is not a "gravity on a lab scale" setup.
Cocoleia said:
then I integrated that to find the position, which is A/m ln(x)
Your position depends on the logarithm of the position?
 
mfb said:
F=ma gives you the acceleration as function of distance. Converting this to acceleration as function of time (what you need for the integration steps) is not trivial.
That does not work. This is not a "gravity on a lab scale" setup.
Your position depends on the logarithm of the position?
Ok. Then how will I find the potential energy ?
 
The definition of potential energy directly gives a way to calculate it based on the force.
 

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