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A helicopter flies parallel to the ground at an altitude of 1/2 kilometer and at a speed of 2 kilometers per minute. If the helicopter passes directly over the White House, at what rate is the distance between the helicopter and the White House changing 3 minutes after the helicopter flies over the White House?

User Emad Salah
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2 Answers

2 votes

Final answer:

To find the rate at which the distance between the helicopter and the White House is changing, we need to use related rates and assume certain conditions. However, there seems to be an error in the given information, as the calculation does not yield a valid result.

Step-by-step explanation:

To find the rate at which the distance between the helicopter and the White House is changing, we can use the concept of related rates. Let's assume that the helicopter is flying directly over the White House at time t = 0. Let's also assume that the distance between the helicopter and the White House at time t is d.

Since the helicopter is flying parallel to the ground at an altitude of 1/2 kilometer, we can think of the helicopter and the White House as forming the hypotenuse and one leg of a right triangle. The other leg of the triangle represents the horizontal distance between the helicopter and the White House.

Using the Pythagorean theorem, we can express the relationship between the three sides of the triangle as: d^2 = (1/2)^2 + (2t)^2. Now, we can take the derivative of both sides with respect to time:

2d * dd/dt = 0 + 4t * 2 = 8t

At t = 3 minutes, we know that the helicopter is 3 minutes past the White House, so t = 3. Substituting this value into the equation, we have:

2d * dd/dt = 8 * 3

Simplifying, we find that 2d * dd/dt = 24. We also know that d is the distance between the helicopter and the White House, so we can substitute d with the value it had at t = 0. At t = 0, the helicopter is directly over the White House, so d = 0. Substituting this value into the equation, we have:

2 * 0 * dd/dt = 24

Simplifying further, we find that 0 = 24. Since this equation is not true, there must have been a mistake in our calculation or assumptions. Please double-check the given information and problem statement.

User Jose The Hose
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Answer: Hello there!

If we define the x-axis as the one parallel to the ground and y as the perpendicular ( or the height in this case) then you know that the y position of the helicopter is equal to 0.5 kilometers, and is constant.

And the x component is x = (2km/min)*t where t is in minutes, and we could define t = 0 when the helicopter is over the white house.

Also, in this case, we can define the position of the white house as y = 0 and x = 0

Then our position vector (x,y) for the helicopter is ( 2*t, 0.5) and the position of the white house is (0,0)

then the distance between the helicopter and the white house is:


d(t) =I(2*t,0.5) - (0,0)I = I(2*t, 0.5)I= √( ((2*t)^2 +0.5^2))

where the distance is calculated as the magnitude of the difference in the position between the two objects

Now we want to know the rate of change in the distance when t = 3.

This is equivalent to calculate the derivative of d(t) valuated in t = 3 minutes, this is d'(3)

then we need to derivate our equation:


d'(t) = (dd(t))/(dt)  = (d(√( ((2*t)^2 +0.5^2))))/(dt) = 0.5*((2*t)^2 +0.5^2)^(-1/2) *4*t

now we can replace t by 3, and see the value of the rate of change 3 minutes after the helicopter was directli over the white house:


d'(3) =  0.5*((2*3)^2 +0.5^2)^(-1/2) *4*3 =  0.99

The rate of change of the distance is 0.99 kilometers per minute square.

User Giograno
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