1. ## Parachute problem

Ok, i'm out of ideas so i figure ill give this a shot.

General equation of a parabola is x(y)=ay^2+by+c, i need x(0)=10 and x(5)=0.
So C must equal 10, and b=-2-5a. So the equation is now x(y)=ay^2-(2+5a)y+10.

Now, from here i must somehow derive the differential equation
(d^2y/dt^2)+(g/(1+(2ay-(2+5a))^2))=0 with y(0)=5 and y'(0)=0.

g=10m/s^2

I know the denominator is the same as 1+(x'^2), but apparently i have no idea how to derive differential equations. So thank you for any help!! I have more information on the problem but i'm not sure what else would be needed for the derivation.

2. Originally Posted by Blankman013
Ok, i'm out of ideas so i figure ill give this a shot.

General equation of a parabola is x(y)=ay^2+by+c, i need x(0)=10 and x(5)=0.
So C must equal 10, and b=-2-5a. So the equation is now x(y)=ay^2-(2+5a)y+10.

Now, from here i must somehow derive the differential equation
(d^2y/dt^2)+(g/(1+(2ay-(2+5a))^2))=0 with y(0)=5 and y'(0)=0.

g=10m/s^2

I know the denominator is the same as 1+(x'^2), but apparently i have no idea how to derive differential equations. So thank you for any help!! I have more information on the problem but i'm not sure what else would be needed for the derivation.
You know, it'd be best to give the entire question ....

You start by talking about x = x(y). Then you start talking about a DE that clearly uses y = y(t). Then you mention x' implying there's a function x = x(t) somewhere ......

If you gave a boundary condition for your DE, why not use it to get further info about the parameters (a dn b) in whatever function is relevant?