How to find trajectory as a function of time with energy

AI Thread Summary
An object with mass m experiences an attractive force F=-A/x^2, leading to the need for calculating its potential energy. The initial approach involved using F=ma to derive acceleration, followed by integrating to find speed and position, resulting in a position function of A/m ln(x). However, challenges arise in converting acceleration from a function of distance to one of time, complicating the trajectory calculation. The potential energy can be derived from the force definition, but the logarithmic position function raises questions about its validity in this context. The discussion highlights the complexities of deriving trajectory as a function of time when dealing with non-standard forces.
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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