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November 9th, 2017, 01:43 PM   #1
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Related rates - bridge / boat

A bridge goes across the river at a height of 60m. A car on the bridge travelling at 40 m/s passes directly over a boat travelling up the river at 15 m/s. Find the rate at which the distance between the car and the boat is increasing 3 seconds later?
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November 10th, 2017, 03:24 AM   #2
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One method: set up a coordinate system so that (0, 0, 0) is the position of the boat directly under the bridge and (0, 0, 60) is the position of the car with the x-axis parallel to the bridge. What are the positions of the boat and car t seconds later? What is the distance between those two points? Differentiate that formula with respect to t to find the rate of change of that distance.
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