river

2 posts / 0 new
Last post
Lyneth Foman-eg
Lyneth Foman-eg's picture
river

A river flows 1.5 miles an hour.(a) In what direction must a man swim in order to go straight across if his rate of swimming in still water is 2.5 miles an hour?(b) How long will it take him to cross the river if it is 1/ mile wide?

Jhun Vert
Jhun Vert's picture

Part (a)
$\sin \theta = \dfrac{1.5}{2.5}$

$\theta = 36.87^\circ$   ←   against the flow of the river
 

alg_002-motion-vector.gif

 

$v^2 + 1.5^2 = 2.5^2$

$v = 2 ~ \text{mph}$
 

$t = \dfrac{s}{v} = \dfrac{1}{2}$

$t = 0.5 ~ \text{hr} = 30 ~ \text{min}$

Add new comment

Deafult Input

  • Allowed HTML tags: <img> <em> <strong> <cite> <code> <ul> <ol> <li> <dl> <dt> <dd> <sub> <sup> <blockquote> <ins> <del> <div>
  • Web page addresses and e-mail addresses turn into links automatically.
  • Lines and paragraphs break automatically.
  • Mathematics inside the configured delimiters is rendered by MathJax. The default math delimiters are $$...$$ and \[...\] for displayed mathematics, and $...$ and \(...\) for in-line mathematics.

Plain text

  • No HTML tags allowed.
  • Lines and paragraphs break automatically.