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A boat begins at point A and heads straight across a 60.0-meter wide river with a speed of 4.0 m/s (relative to the water). The river water flows north at a speed of 3.0 m/s (relative to the shore). The boat reaches the opposite shore at point C. It will take the boat ...
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For a boat that heads straight across a river, the distance (dacross) which it travels across (river width) is mathematically related to the time (t) to cross the river and the boat velocity (vboat) in accordance with the formula:
dacross= vboat• t
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For a boat heading straight across a river, it is the boat velocity and the river width that affect the time of travel. The time of travel is dependent solely upon how far across the river the boat must travel and the speed at which it is traveling across the river (see Formula Frenzy section). The speed of the river, being directed parallel to the river's banks will have no effect upon the time to travel perpendicular to the river's banks. As it is often said, perpendicular components of motion are independent of each other.
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