1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Velocity and displacement question

  1. Sep 21, 2005 #1

    Steven-

    User Avatar

    Swimming at 0.15 m/s relative to still water, a swimmer heads directly across a 100-m-wide river. He arrives 50 m downstream from a point directly across the river from his starting point.
    a) What is the speed of the current in the river?
    b) In what direction should the swimmer head so as to arrive at a point directly opposite his starting point?

    I got 13.3 meters/second for part (a). Can someone check this?
    For part (b), I am unsure of what to do. Can someone give me a hint in the right direction?
     
    Steven-, Sep 21, 2005
  2. jcsd
    Phys.org - latest science and technology news stories on Phys.org
  3. Sep 21, 2005 #2

    JoAuSc

    User Avatar

    For part b: If the swimmer wanted to stay in one place, how fast would he have to swim? In what direction? Hopefully, this speed is less than the swimmer's stop speed, otherwise there'd be no way he could swim across without being swept downstream. This leads me to believe your answer for part a of 13.3 m/s is incorrect. Besides, 13.3 m/s is a very fast speed for a river.
     
    JoAuSc, Sep 21, 2005
  4. Sep 21, 2005 #3

    whozum

    User Avatar

    Your answer for (a) is correct, for b, try using a vector approach.
     
    whozum, Sep 21, 2005
  5. Sep 21, 2005 #4

    JoAuSc

    User Avatar

    (a) can't possibly be correct. If there were no current, the swimmer would cross the river in 100/0.15 = about 600 seconds. In the same time, a current of 13.3 meters/s would sweep the guy 8000 meters downstream.
     
    JoAuSc, Sep 21, 2005
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook




Loading...
Similar Threads for Velocity displacement question Date
2 Questions about motion in 1 direction Sep 23, 2015
Displacement and Velocity Question Jun 11, 2014
Displacement/ Velocity/ Acceleration Clock Question Nov 1, 2012
Aeroplane flight: time, displacement, velocity question Jan 9, 2011
I need help with this question on velocity/displacement Feb 1, 2009