Review 1: a plane is located x = 40 miles (horizontally) away from an airport at an altitude of h miles. radar at the airport detects that the distance s(t) between the plane and airport is changing at the rate of s(t) = −240 mph. if the plane flies toward the airport at the constant altitude h = 4, what is the speed |x(t)| of the airplane?

Explanation:

Let h is the height of the plane above ground. x is the horizontal distance between the ground and the airport. Let s(t) is the distance between the plane and the airport. So,

...........(1)

Given, h = 4, x = 40 and s(t) = -20 mph

Differentiate equation (1) wrt t

When x = 40,

So, the speed of the airplane is 241.14  m/s. Hence, this is the required solution.

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