Kinematics - trajectory formula

In summary, the conversation is about finding the trajectory formula and using trigonometric identities to simplify the equation. The final solution is a parabolic figure represented by the equation ## y= - \frac{2}{a}x^2+a ##.
  • #1
quas
7
1

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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  • #2
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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  • #3
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
 
  • #4
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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  • #5
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?
 
  • #6
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}##.
 
  • #7
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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  • #8
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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Likes quas

1. What is the equation for trajectory in kinematics?

The trajectory equation in kinematics is given by y = y0 + tanθ * x - gx^2 / (2v0^2 * cos^2θ), where y is the height, y0 is the initial height, θ is the angle of projection, x is the horizontal distance, g is the acceleration due to gravity, and v0 is the initial velocity.

2. How is trajectory calculated in kinematics?

Trajectory in kinematics is calculated using the equation y = y0 + tanθ * x - gx^2 / (2v0^2 * cos^2θ). This equation takes into account the initial height, angle of projection, horizontal distance, acceleration due to gravity, and initial velocity to determine the trajectory of an object.

3. What is the significance of the trajectory formula in kinematics?

The trajectory formula in kinematics is significant because it allows us to predict the path of a moving object in two dimensions. By plugging in the initial conditions, we can determine the trajectory of an object and analyze its motion.

4. How does the trajectory of an object change with different initial conditions?

The trajectory of an object changes with different initial conditions because the trajectory formula takes into account the initial height, angle of projection, and initial velocity. If any of these values change, the trajectory will also change. For example, increasing the initial velocity will result in a longer and flatter trajectory, while increasing the angle of projection will result in a higher and shorter trajectory.

5. Can the trajectory formula be used for non-uniform motion?

Yes, the trajectory formula can be used for non-uniform motion. However, it is important to note that this formula assumes a constant acceleration due to gravity. If the acceleration is not constant, the trajectory formula will need to be modified to accurately predict the trajectory of the object.

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