AP Physics 1· difficulty 4/5
A river of width flows with speed . A boat moves at speed relative to water. To minimize the time to reach the far bank, the boat must aim straight across (perpendicular to the banks). What is the minimum crossing time and how far downstream does the boat land?
time , drift
time , drift
time , drift
time , drift
Explanation
Aiming perpendicular gives the largest cross-stream component , so the time is . During that time the current carries the boat a distance downstream.
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