How to find trajectory as a function of time with energy

In summary, the conversation discussed finding the potential energy of an object with a given mass and attractive force. The solution involved using the equation F=ma to find the acceleration, integrating to find the speed and then the position. However, there was some confusion about the use of potential energy in this scenario.
  • #1
Cocoleia
295
4

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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  • #2
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?
 
  • #3
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 ?
 
  • #4
The definition of potential energy directly gives a way to calculate it based on the force.
 

Related to How to find trajectory as a function of time with energy

1. What is the formula for calculating trajectory as a function of time with energy?

The formula for calculating the trajectory as a function of time with energy is:
t = (2 * v * sinθ)/g
Where t is time, v is initial velocity, θ is launch angle, and g is the acceleration due to gravity.

2. How does energy affect the trajectory of an object?

Energy plays a crucial role in determining the trajectory of an object. The kinetic energy of an object determines its velocity, which in turn affects the range and height of its trajectory. The potential energy of an object also affects its trajectory, as objects with more potential energy will have a steeper trajectory.

3. Can you find the trajectory of an object without knowing its energy?

No, it is not possible to accurately calculate the trajectory of an object without knowing its energy. The energy of an object is a crucial factor in determining its trajectory, as it affects both the velocity and angle of launch.

4. How does changing the launch angle affect the trajectory of an object?

Changing the launch angle of an object can greatly affect its trajectory. A higher launch angle will result in a higher peak height and a shorter range, while a lower launch angle will result in a lower peak height and a longer range. The optimal launch angle for maximum range is 45 degrees.

5. What is the significance of finding the trajectory as a function of time with energy?

Finding the trajectory as a function of time with energy allows us to accurately predict the path of an object based on its initial energy. This is important in fields such as physics and engineering, where understanding the trajectory of objects is crucial for designing and predicting the behavior of systems.

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