KinematicsHard
Question
A river of width 200 m is flowing from west to east with a speed of $18\text{ }km/h$. A boat, moving with speed of $36\text{ }km/h$ in still water, is made to travel one-round trip (bank to bank of the river). Minimum time taken by the boat for this journey and also the displacement along the river bank is
$\_\_\_\_$ and $\_\_\_\_$ respectively.
Options
A.20 s and 100 m
B.40 s and 0 m
C.40 s and 200 m
D.40 s and 100 m
Solution
Minimum time :
$$t_{\text{min~}} = \frac{200}{10} = 20sec $$For round trip $= 40sec$.
Displacement along river bank $= 40 \times 5 = 200\text{ }m$
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