Kinematics - trajectory formula

AI Thread Summary
The discussion focuses on deriving the trajectory formula in kinematics using trigonometric identities. Participants explore relationships between variables x and y, utilizing identities like sin and cos to express these relationships. A key point is the transformation of sin(ωt) into x/a, which simplifies the equations. The final derived equation is confirmed to represent a parabolic trajectory. The collaborative effort emphasizes the importance of correctly applying trigonometric relationships to achieve the desired formula.
quas
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Homework Statement


given :
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i need to find the trajectory formula

Homework Equations


i'm not sure if to use :
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The Attempt at a Solution


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I tried different options with the trigonometric identities that I have written before:
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thanks
 
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quas said:

The Attempt at a Solution


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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?

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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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