Projectile motion with aerodynamic drag force

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Homework Help Overview

The discussion revolves around a projectile motion problem involving aerodynamic drag force. The projectile has a mass of 1300 kg and is launched with initial velocity components of 108 m/s in both the x and y directions. The drag force is defined as C(V)^2, with C being 0.6. Participants are exploring how to calculate the range and angular momentum of the projectile under these conditions.

Discussion Character

  • Mixed

Approaches and Questions Raised

  • The original poster attempts to calculate the velocity and weight, and expresses confusion about the aerodynamic drag force and its components. They question the assumption of a 45-degree launch angle and seek guidance on finding angular momentum. Other participants suggest using numerical methods and applying Newton's second law to derive differential equations for the motion.

Discussion Status

The discussion is ongoing, with participants exploring various interpretations of the problem. Some guidance has been offered regarding the application of Newton's second law and the numerical approach to solving the equations, but there is no explicit consensus on the next steps.

Contextual Notes

There is a noted uncertainty regarding the complexity of the problem, as it may not be solvable analytically. The original poster expresses frustration with their understanding and considers whether the question is appropriate for the current forum level.

IceD
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Homework Statement



A projectile of mass 1300kg is launched from the ground (x =0, y =0)
initial velocity components Vx=Vy=108m/s
aerodynamic drag force is of magnitude C(V)^2
where C = 0.6

Homework Equations



Finding the range and angular momentum initial and final


The Attempt at a Solution


1. I found V = 152.74 (*by V= root(Vx^2 + Vy^2)
2. and weight as 12753 kg
3. I tried to find aerodynamic drag force (FD), but I got something like 13997.70 m^2/s^2
(it should be in Newtons right?)
4. I think I'll break FD to x and y components and use them to calculate when it'll reach it's peak (Vy= 0) and based on it I'll use the the t to get the distance...but how to find it?
5. for the angle, can I assume that it was 45 degrees angle?
since Vx=Vy?
6. and I have no idea how to find the angular momentum @.@

Sorry if my working is quiet "useless" cause I'm quiet "blind" at this subject...

Thanks before :D

Regards,
IceD
 
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This question is not a trivial one and indeed, cannot be solved analytically in terms of elementary functions. You can however, solve the system numerically.

As you say, you need to apply Newton's second law to each component (horizontal and vertical) of the motion. This will then yield a system of two coupled differential equations that you will need to sole numerically.

As I said, this problem isn't straightforward and the fact that you have posted this in the Introductory Physics forums would suggest that you are still in elementary physics classes. So I must as, are you sure that you have the question correct? How much numerical analysis have you done?
 
yes, I'm sure that the question is correct @.@
I found the V and the W... but can't go any further than that @.@
huff...
so should I post this question in advance physics section?
 
IceD said:
yes, I'm sure that the question is correct @.@
I found the V and the W... but can't go any further than that @.@
huff...
so should I post this question in advance physics section?
Have you tried to write down the two PDEs from Newton's Second law?

I think that your question is fine here, but I can move it for you if you wish.
 

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