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 Kinematics and Dynamics Kinematics and Dynamics Physics Help Forum Sep 20th 2019, 01:24 PM #1 Junior Member   Join Date: Sep 2019 Posts: 3 Yacht problem The entrance to a harbour is a channel of length A which runs between two banks a distance B apart. The banks and the channel can be assumed to be rectangular. There is a current flowing with a speed v from one bank to the other. A yacht travelling at a constant speed relative to the water u wants to enter the harbour. Find the minimum value of u for the yacht to safely enter the harbour. Express u in terms of v,A and B Need help solving this. I keep getting told we cannot assume the yacht is perpendicular to the water flow   Sep 22nd 2019, 05:05 AM #2 Senior Member   Join Date: Jun 2016 Location: England Posts: 1,060 The velocity of the yacht must be such that over the distance A the current v will push it sideways by the distance B. Find the (equation for the) time taken for the flow v to push the yacht a distance of B find the (equation for the) speed (along the channel) required for the yacht to move the Distance A in that time. This gives you (the equations for) two (perpendicular) velocities add (the equations for) these two velocities to get the (equation for the) total velocity of the yacht. __________________ ~\o/~ Last edited by Woody; Sep 22nd 2019 at 05:08 AM.  Tags problem, yacht Thread Tools Show Printable Version Email this Page Display Modes Linear Mode Switch to Hybrid Mode Switch to Threaded Mode