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physstudent1
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Homework Statement
A flagpole 40 ft high stands on level ground. A flag is attached to a 120 ft rope passing through a pulley at the top of the flagpole. The other end of the rope is tied to a car at ground level. If the car is driving directly away from the flagpole at 3ft/sec, how fast is the flag rising when the top of the flag is 20 ft off the ground.
Homework Equations
The Attempt at a Solution
I used z for the hypotenuse x for the flat leg and y for the vertical leg, I used the fact that the rope is 120 ft to set up z = 120-y where y is how far the flag has risen. So i got (120-y)^2 = x^2 + y^2 I took the derivative ended up with -240dy/dt = 2x(dx/dt) and plugged knowns into get dy/dt of -2.5 can anyone help?