need help-been stuck on this question for 30 mins (model rocket)

[shadowman123]

A person is standing 350 feet away from a model rocket that is fired straight up into the air at a rate of 15ft/sec. At what rate is the distance between the person and the rocket increasing (a) 20 seconds after liftoff? (b) 1 minute after liftoff?

So far I have drawn a triangle with sides x,y and h.
I did:
x^2+y^2=h^2
did the derivative to get
2x(dx/dt)+2y(dy/dt)=2h(dh/dt)
I don't know what to do next.

 

[Deleted member 4993]

A person is standing 350 feet away from a model rocket that is fired straight up into the air at a rate of 15ft/sec. At what rate is the distance between the person and the rocket increasing (a) 20 seconds after liftoff? (b) 1 minute after liftoff?

So far I have drawn a triangle with sides x,y and h.
I did:
x^2+y^2=h^2
did the derivative to get
2x(dx/dt)+2y(dy/dt)=2h(dh/dt)
I don't know what to do next.

First thing you need to do is to define your variables.

What does x, y & h represent in this situation?

What variable represent the distance between the rocket and the person?

 

[Steven G]

A person is standing 350 feet away from a model rocket that is fired straight up into the air at a rate of 15ft/sec. At what rate is the distance between the person and the rocket increasing (a) 20 seconds after liftoff? (b) 1 minute after liftoff?

So far I have drawn a triangle with sides x,y and h.
I did:
x^2+y^2=h^2
did the derivative to get
2x(dx/dt)+2y(dy/dt)=2h(dh/dt)
I don't know what to do next.

After you define YOUR variables, as you were already instructed to do, do you know the exact value of any of them even as things are changing???

What is it that you are trying to find? You really can't (and should NOT) do anything unless you know what your goal is.

 

[shadowman123]

Well I have gotten
x= 350
dy/dt= 15ft/s
and i am trying to find dh/dt


However in the formula i need to find 1 more variable so I can use it in the derivative equation I have

 

[Steven G]

Well I have gotten
x= 350
dy/dt= 15ft/s
and i am trying to find dh/dt


However in the formula i need to find 1 more variable so I can use it in the derivative equation I have

You really should define your variables.

Why do you think that you need 1 more variable?

Can you think of an equation that relates to this problem that only only x, y and h in it. If yes, then take the derivative of it and solve for dh/dt.

If x=350, then what is dx/dt equal to?

 

[shadowman123]

I am sorry but I still can not figure out what im missing :/

 

[Steven G]

I am sorry but I still can not figure out what im missing :/

You already have an equation that has dh/dt, so go and solve for it. Then (or if you prefer, 1st) put in the know values. Then come back here with that result.