Kinematics - trajectory formula

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Homework Help Overview

The original poster seeks to find the trajectory formula in the context of kinematics, specifically involving trigonometric identities and their relationships to the variables involved.

Discussion Character

  • Exploratory, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Participants discuss various trigonometric identities and their potential relationships to the trajectory formula. There are attempts to express variables in terms of each other, and questions arise about the correctness of these relationships.

Discussion Status

Some participants have provided guidance on simplifying expressions and have pointed out potential mental blocks in understanding the relationships between the variables. There is an ongoing exploration of how to manipulate the equations to arrive at a parabolic form.

Contextual Notes

There appears to be some uncertainty regarding the application of trigonometric identities and the correct substitutions to use in the equations. The discussion includes attempts to clarify these points without reaching a definitive conclusion.

quas
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Homework Statement


given :
1409395.jpg
i need to find the trajectory formula

Homework Equations


i'm not sure if to use :
6687766.jpg


The Attempt at a Solution


6325967.jpg
[/B]
I tried different options with the trigonometric identities that I have written before:
8541126.jpg

thanks
 
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quas said:

The Attempt at a Solution


6325967.jpg
[/B]

If ##x## and ##y## are as above, can you not find a simple relationship? You've already quoted the relevant trig identity somewhere.
 
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PeroK said:
If ##x## and ##y## are as above, can you not find a simple relationship? You've already quoted the relevant trig identity somewhere.

do you mean?

9133966.jpg
 
quas said:
do you mean?

9133966.jpg

No, I meant:

##\frac{y}{a} = \cos(2 \omega t) =## something to do with ##\sin(\omega t) =## something to do with ##\frac{x}{a}##

You're terribly over-complicating this.
 
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PeroK said:
No, I meant:

##\frac{y}{a} = \cos(2 \omega t) =## something to do with ##\sin(\omega t) =## something to do with ##\frac{x}{a}##

You're terribly over-complicating this.

Ok I can write ##\frac{y}{a} =1-2sin^2(\omega t) ##, also to ## \frac{x^2}{a^2}\ = sin^2(\omega t) ## and then insert ## sin^2(\omega t) ##
to the equation ##\frac{y}{a} =1-2sin^2(\omega t) ## . would it be correct?
 
quas said:
Ok I can write ##\frac{y}{a} =1-2sin^2(\omega t) ##, also to ## \frac{x^2}{a^2}\ = sin^2(\omega t) ## and then insert ## sin^2(\omega t) ##
to the equation ##\frac{y}{a} =1-2sin^2(\omega t) ## . would it be correct?

You seem to have a mental block about replacing ##\sin(\omega t) ## by ##\frac{x}{a}##.
 
PeroK said:
You seem to have a mental block about replacing ##\sin(\omega t) ## by ##\frac{x}{a}##.
first of all thanks for your help it's not taken for granted
Last try:
in the end I will get : ## \frac{2x^2}{a^2}+ \frac{y}{a}=1 ## then : ## y= - \frac{2}{a}x^2+a ## and that's parabola figure . right ?
 
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quas said:
first of all thanks for your help it's not taken for granted
Last try:
in the end I will get : ## \frac{2x^2}{a^2}+ \frac{y}{a}=1 ## then : ## y= - \frac{2}{a}x^2+a ## and that's parabola figure . right ?

It is!
 
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