Trajectory of projectile with considerable drag

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Discussion Overview

The discussion revolves around the mathematical formulation of the trajectory of a projectile experiencing drag that is proportional to the square of its velocity. Participants are exploring the equations of motion and seeking assistance in solving the resulting system of differential equations.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Homework-related

Main Points Raised

  • One participant presents a set of equations governing the motion of a projectile under the influence of drag and gravity, specifying initial conditions.
  • Another participant reformulates the equations and questions the level of education for which assistance should be aimed, suggesting clarity on the trajectory representation.
  • A third participant references a previous discussion on a similar problem, indicating that this issue has been addressed before.
  • A later reply reiterates the previous reference while emphasizing the need for assistance in solving the mathematical aspects of the problem.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the method to solve the equations, and multiple views on the approach to the problem are present. The discussion remains unresolved regarding the specific solution to the equations.

Contextual Notes

Participants express uncertainty regarding the appropriate coordinate system to use and the complexity of the differential equations involved. There is a lack of clarity on the educational background of the original poster, which may influence the type of assistance provided.

HP007
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Facing some horrible mathematical situation while solving to find equation of trajectory of projectile when drag is proportional to v^2.
my equations where i end up with are as follow:
equation 1:
mdv/dt=(-kv^2)+(-mgsinγ);
equation 2:
(-mv)dγ/dt=mgcosγ;
equation 3:
dx/dt=vcosγ;
equation 4:
dy/dt=vsiny;
where:
v is velocity of particle at instance when it makes an angle γ with horizontal plane.
Initial condition is known and assume it to be u at an angle α.
please assist me in solving this.
 
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(1) ##m\dot v = -kv^2-mg\sin\gamma##
(2) ##-mv\dot \gamma = mg\cos\gamma##
(3) ## \dot x = v\cos\gamma##
(4) ## \dot y = v\sin\gamma##

Whence ##v(0)=u## and ##\gamma(0)=\alpha##

Do you want the trajectory: (x(t),y(t))?

Have you ever tried to solve systems of differential equations before?
(i.e. what is the level of education help should be aimed at?)

Have you seen:
http://users.df.uba.ar/sgil/physics_paper_doc/papers_phys/mechan/air0.pdf

You seem to be trying to use cartesian and some sort of polar coordinates at the same time - it is best practice to pick just one coordinate system and stick to it.
 
Last edited by a moderator:
Nugatory said:
This problem has come up before. Try this thread: https://www.physicsforums.com/showthread.php?t=712807


But I have already arrived at those set of coupled equations I want to know the way to solve it.
Assist me in solving mathematical part of the problem.
 

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