Solving Rectilinear Motion Problem Involving Model Rocket

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Sara launches a model rocket in an open field near her house. Its trajectory is described by the function y=60ln(x+1)-6x for x=[0,36.15] where y is the rocket's height (in feet) above the ground and x is the horizontal distance (in feet) between the launch site and a point directly below the rocket.

Given that the rocket's horizontal velocity (dx/dt) is 50 ft/s when it's directly over a point 20 (horizontal) feet from the launch site, determine the rocket's vertical veloctiy (dy/dt) at that point.

I don't know how to go about solving this question, because normally the position is given as a function of time. Can someone help me? Thanks.
 
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Chain rule!

dy/dt = ?
find this and do value substitutions
 
rootX said:
Chain rule!

dy/dt = ?
find this and do value substitutions

oh yeah! i was overthinking it way too much. thanks though!
 
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