- #1

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What would you do to find the Parametric equation? Thanks.

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- Thread starter DrummingAtom
- Start date

- #1

- 658

- 2

What would you do to find the Parametric equation? Thanks.

- #2

jgens

Gold Member

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How about these parametric functions.

y = t^2 + t - 3

x = t

y = t^2 + t - 3

x = t

- #3

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Then they said from this we obtain the parametric equations:

x = 24(sqrt2)(t)

y = -16t^2 + 24(sqrt2)(t)

I'm pretty lost on to how they got those ones.

- #4

jgens

Gold Member

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- #5

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- #6

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All they did for y was replace x in the equation with 24(sqrt2)(t). You can do whatever you want to x, as long as you then make sure y and x satisfy the equation.

Then they said from this we obtain the parametric equations:

x = 24(sqrt2)(t)

y = -16t^2 + 24(sqrt2)(t)

I'm pretty lost on to how they got those ones.

- #7

- 658

- 2

All they did for y was replace x in the equation with 24(sqrt2)(t). You can do whatever you want to x, as long as you then make sure y and x satisfy the equation.

Yeah, I understand that part. Maybe I'm not being clear. The whole example is about a projectile that is shot at an angle of 45 degrees and a initial velocity of 48 ft/sec. Then they say it follows the path given by y = -x^2/72 + x

They go on and say how this equation does not give all the information possible. Then how we need to introduce a third variable t for time. Then they by writing x and y as functions of t we get:

x = 24(sqrt2)(t)

y = -16t^2 + 24(sqrt2)(t)

That's where I'm confused, they don't explain how they got to that point (Mathematically).

- #8

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They are using the additional physical information to get the horizontal speed of the particle, so that they can replace x with x(t). Being fired at a 45 degree angle, the horizontal and vertical components of the velocity are the same, as vYeah, I understand that part. Maybe I'm not being clear. The whole example is about a projectile that is shot at an angle of 45 degrees and a initial velocity of 48 ft/sec. Then they say it follows the path given by y = -x^2/72 + x

They go on and say how this equation does not give all the information possible. Then how we need to introduce a third variable t for time. Then they by writing x and y as functions of t we get:

x = 24(sqrt2)(t)

y = -16t^2 + 24(sqrt2)(t)

That's where I'm confused, they don't explain how they got to that point (Mathematically).

Using the kinematic equation for constant velocity (since there is no horizontal acceleration), we get x = v

- #9

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Yay, thanks.

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