Courses
Courses for Kids
Free study material
Offline Centres
More
Store

# A battalion of soldiers is ordered to swim across a river 500 m wide. At what minimum rate should they swim perpendicular to river flow in order to avoid being washed away by the waterfall 300 m downstream. The speed of current being $3{\text{m/sec}}$:A) $6\,{\text{m/sec}}$B) $5\,{\text{m/sec}}$C) ${\text{4}}\,{\text{m/sec}}$D) $2\,{\text{m/sec}}$

Last updated date: 13th Jun 2024
Total views: 52.2k
Views today: 1.52k
Verified
52.2k+ views
Hint: In this solution, we will first calculate the time required by the soldiers to be displaced 300 metres downstream. The speed of the soldiers must be such that they can cross the river in this amount of time.
Formula used: In this solution, we will use the following formula:
$v = \dfrac{d}{t}$ where $v$ is the velocity of an object, $d$ is the distance it travels, and $t$ is the time.

We’ve been given that a battalion of soldiers is ordered to swim across a river 500 m wide perpendicular to it such that they can avoid being washed by the current to the waterfall that is 300 m downstream.
$t = \dfrac{d}{v}$
$\Rightarrow t = \dfrac{{300}}{3} = 100\,s$
$v = \dfrac{{500}}{{100}}$
$\Rightarrow v = 5\,{\text{m/s}}$
Hence they need to have a velocity of $5\,{\text{m/sec}}$ so the correct choice is option (B).