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 arybhatta01 June 9th, 2018 09:33 PM

Relative velocity

While a boat cruises down a river, it crosses a wooden log at a particular point of time. Then the boat travels along the river for a time C and reverses its direction to travel upstream for a time T, when it meets the same wooden log, which has been freely drifting along the river all the while. If the engine of the boat has been working at the same power level throughout its journey, express T in terms of C.

My answer came out: T = C.

Could anyone please confirm as the answer given is roman Tau.

 romsek June 9th, 2018 09:54 PM

Let the boat meet the log the first time at \$t=0\$

Also let the boat's velocity in still water be \$v_b\$

The log drifts at the velocity of the current \$v_c\$

\$C(v_b + v_c) + T(v_c-v_b) = v_c (C+T)\$

This does simplify to \$T=C\$

 arybhatta01 June 9th, 2018 10:02 PM

Many Thanks . I got confused with the answer given in the book.

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