More or less?

Classical Mechanics Level 2

Oarsman A rows on a river, x x miles with the current and x x miles against the current. Oarsman B rows 2 x 2x miles on a lake where there is no current. Which oarsman takes more time: A or B? (Their rowing strength is the same.)

B They will both take the same time A

Richard Plender by Richard Plender , 28, United Kingdom

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3 solutions

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Ne-ko Nya
Aug 29, 2015

If we assume the c o u n t e r c u r r e n t ≥ r o w i n g s t r e n g h t counter \ \ current \geq rowing_ \ \ strenght

then A will take forever to row back.

but B will not have this issue.

Answer : A takes longer

1 Helpful 0 Interesting 0 Brilliant 0 Confused
Richard Plender
Aug 26, 2015

Without algebra:

A on the river will be slower, because the current helps him for less time (he is covering the same distance faster) than it hinders him. If the current is half as fast as his rowing, for example, it will take him as long to do half the trip upstream as it takes B to do the whole trip. And if the current is as fast as his rowing he won't make it upstream at all.

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