I proved a physics equation. Does any one know if theirs an equation like this?

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Discussion Overview

The discussion revolves around a physics problem involving the direction a plane must fly to reach a destination while accounting for wind velocity. Participants explore the mathematical derivation of the relevant equations and the implications of their findings, touching on vector addition and the nature of proofs in physics versus mathematics.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant presents a detailed mathematical derivation to determine the direction and velocity of a plane relative to the ground, incorporating wind effects.
  • Another participant comments on the terminology used, stating that one cannot "prove" anything in physics, only in mathematics.
  • A participant expresses their inexperience in physics, indicating they are in grade 11 and have not yet taken the subject.
  • One participant suggests that the method used for the derivation is overly complex for what is essentially a vector addition problem.
  • Another participant mentions the potential use of sine and cosine laws in solving such problems.
  • A later reply references a historical tool, a circular slide rule, that was once used to solve similar problems, indicating a long-standing interest in the topic.

Areas of Agreement / Disagreement

Participants express differing views on the complexity of the mathematical approach presented, with some suggesting it is unnecessarily complicated while others defend their method. There is no consensus on the correctness of the derivation or the terminology used regarding proofs in physics.

Contextual Notes

The discussion includes various assumptions about the definitions of terms and the mathematical steps involved, which remain unresolved. The complexity of the derivation and its relation to basic vector addition is also a point of contention.

Ambrose 2014
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Direction of a plane proof
48. A pilot wants to land at a small lake that is [N30.0 ̊W] of the airport that she is starting from. The wind has a velocity of 25.0 m/s[W] and the air speed of the plane is 1.90 × 10^2 m/s . What direction will the plane have to fly to get to its destination? What will be the velocity of the plane relative to the ground?

vt as the speed you'll achieve .
x as the plane speed or velocity.
w as wind speed or velocity.
Θ as the angle the plane has to go to achieve angle Φ at vt speed.
Φ as the angle away from start.

Know start to take the big picture coloured in red
vt^2=(xsinΘ+w)^2+(xcosΘ)^2
vt^2=(x^2sinΘ^2+wxsinΘ+wxsinΘ+w^2)+(x^2cosΘ^2)

now we have to get rid of the cosΘ^2 by taking(in green)
x^2=(x^2sinΘ^2)+(x^2cosΘ^2)
With x^2 divided
x^2/x^2=(x^2sinΘ^2)/x^2+(x^2cosΘ^2)/x^2
1=sinΘ^2+cosΘ^2
1-cosΘ^2=sinΘ^2
Now sub into the red coloured equation

vt^2=x^2(1-cosΘ^2)+wxsinΘ+wxsinΘ+w^2)+(x^2cosΘ^2)
vt^2=(x^2-x^2cosΘ^2)+(wxsinΘ+wxsinΘ+w^2)+(x^2cosΘ^2)
vt^2=x^2+2wxsinΘ^2+w^2

Now look at what's coloured in blue which is used to get rid of vt
sinΦ=(xsinΘ+w)/vt
(vt=(xsinΘ+w)/sinΦ)^2
vt^2=(x^2sinΘ^2+wxsinΘ+wxsinΘ+w^2)/sinΦ^2

Now we sub this equation into the red and green equation

(x^2sinΘ^2+2wxsinΘ+w^2)/sinΦ^2=x^2+2wxsinΘ+w^2

Move everything over to left

(x^2sinΘ^2/sinΦ^2)+(2wxsinΘ/sinΦ^2-2wxsinΘ)
(+w^2sinΦ^2-x^2-w^2)=0
A B C
Use the quadratic formula
sinΘ=-(2wx/sinΦ^2-2wx)+/-square root((2wx/sinΦ^2-2wx)^2-4x^2/sinΦ^2(w^2/sinΦ^2-x^2-w^2)/2x^2/sinΦ^2

sinΘ=(-2wx/sinΦ^2+2wx)+/-square root((4x^2w^2/sinΦ^4-4w^2x^2/sinΦ^2-4w^2x^2/sinΦ^2+4w^x^2)(-4x^2w^2/sinΦ^4+4x^4/sinΦ^2+4w^2x^2/sinΦ^2))/2x^2/sinΦ^2

sinΘ=(-2wx/sinΦ^2+2wx)+/-square root((-4w^2x^2/sinΦ^2+4w^x^2+4x^4/sinΦ^2))/2x^2/sinΦ^2

sinΘ=(-2wx/sinΦ^2+2wx)+/-square root((-4w^2x^2+4x^4)/sinΦ^2+4w^2x^2)/2x^2/sinΦ^2

multiply the whole equation by sinΦ^2
sinΘ=(-2wx+2wxsinΦ^2)+/-square root((-4w^2x^2+4x^4)sinΦ^2+4w^2x^2sinΦ^4)/2x^2
divid the equation by 2

sinΘ=(-wx+wxsinΦ^2)+/-
square root((-w^2x^2+x^4)sinΦ^2+w^2x^2sinΦ^4)/x^2
Divid by x
sinΘ=(-w+wsinΦ^2)+/-square root((-w^2+x^2)sinΦ^2+w^2sinΦ^4)/x

now say + not +/- and factor out sinΦ out of what's in the
Square root since we don't want a negative angle.

sinΘ=(-w+wsinΦ^2)+square root((-w^2+x^2+w^2sinΦ^2))sinΦ/x
Also written as

sinΘ=square root((-w^2+x^2+w^2sinΦ^2))sinΦ+(-w+wsinΦ^2)/x
if wind is in y direction
cosΘ=square root((-w^2+x^2+w^2cosΦ^2))cosΦ+(-w+wcosΦ^2)/x

x>w
If wind is going to opposite your going make negative.
 
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Just as an aside on your problem, addressing your terminology. You cannot "prove" anything in physics, only in math, so if you proved it, it's math. Physics is always subject to disproof, math not so much.
 
Thank you for the advice I'm only in grade 11 and I didn't take physics yet
 
Ambrose 2014 said:
Thank you for the advice I'm only in grade 11 and I didn't take physics yet

Well, welcome to the forum
 
Hey thanks and this is my first time posting so that's why I didn't know what section to put my formula question in and by the way this is only for x direction the other one for cos I proved mathematically on paper but didn't type up yet.
 
It maybe long but I did so I can create an equation to solve problems like this since I like using equation and wouldn't sin and cosine laws work too
 

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