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A train is traveling on a straight track passing through an open plain at the speed of 1.5 mile/minute. A camera located 1 mile from the train track is filming the train starting at the time when the train is the closest to the camera as it speeds away.

a. How fast is the train's distance from the camera changing when the train is 2 miles from the camera?

User Adzz
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Final answer:

When the train is 2 miles away from the camera, the distance between the train and the camera is increasing at a rate of 3/sqrt(5) miles per minute.

Step-by-step explanation:

Rate of Change in Distance From the Camera to the Train

Let's visualize the scenario where a train is moving away from a camera on a straight track at 1.5 miles per minute, and we want to find out how fast the distance from the camera to the train is changing when the train is 2 miles away from the camera. To solve this problem, we can apply the Pythagorean theorem to a right triangle formed by the camera, the point on the track closest to the camera, and the train's position when it is 2 miles away from the camera.

The distance of the camera from the track is 1 mile, and the distance of the train from the point of closest approach is now 2 miles. Using derivatives and the Pythagorean theorem, we get:

  • Let x be the distance of the train from the point on the track closest to the camera.
  • Let y be the distance from the camera to the train.
  • Pythagorean theorem: x^2 + 1^2 = y^2.
  • When x is 2 miles, y can be found by calculating y = sqrt(2^2 + 1^2) = sqrt(5), so the distance is sqrt(5) miles.
  • We differentiate both sides of the equation with respect to time t to find dy/dt when x is 2 miles.
  • 2x(dx/dt) = 2y(dy/dt) after differentiation.
  • Solving for dy/dt when x = 2 miles and dx/dt = 1.5 miles/minute, we find that dy/dt = (2 * 2 * 1.5) / (2 * sqrt(5)) = 3/sqrt(5) miles/minute, which is the rate at which the distance from the camera to the train is changing.

Therefore, when the train is 2 miles away from the camera, the distance between them is increasing at a rate of 3/sqrt(5) miles per minute.

User Carlos F
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