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Here is a problem from lecture notes:

Projectile is fired with initial velocity v from the ground, at an angle of theta. Its trajectory is parameterized:

x = vt cos theta

y = vt sin theta - 1/2 gt^2

 

t = time, g = acceleration due to gravity.

 

A parabolic arch is formed by the projectile. The maximum area under the trajectory is given by k x v^4 / g^2 where k is a constant. Find k.

 Dec 24, 2021
 #1
avatar+117467 
+1

This question doesn't quite make sense to me.

if v is a set constant but theta is variable (which is not stated)

then I got the max area when theta = pi/6

 

The max area would be   \(\frac{\sqrt3}{24}*\frac{v^4}{g^2}\)

 

 

I have not checked my working and it could easily be wrong but it is at least in the form that is asked for.

 

If you want to ask questions feel free to do so.

 Dec 24, 2021
 #2
avatar+72 
+1

The form of the answer is correct but it seems like the constant k is a bit off.

Thanks

jsaddern  Dec 24, 2021
 #3
avatar+117467 
+1

Did you just put the answer in an answer box to get a right-wrong answer?

Melody  Dec 25, 2021
 #4
avatar+117467 
+1

This answer seems less likely and more prone to error but on a second attempt I got

 

\(Max = \frac{(33-9\sqrt{13})\sqrt{6\sqrt{13}-18}}{6}\:\displaystyle \frac{v^4}{g^2}\)

 

 

 

Do you know the actual answer by any chance?

 Dec 25, 2021

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