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: Motion in 2 Directions: An Algebraic Approach

  1. Oct 30, 2016 #1
    1. The problem statement, all variables and given/known data
    A swimmer jumps into a 5.1 km river and swims straight to the other side at 0.87 km/h [N].
    There is a current in the river of 2.0 km/h [W]
    a)How long does it take the swimmer to reach the other side?
    b)How far downstream has the current moved her by the time she reaches the other side?

    2. Relevant equations
    v= d/t
    3. The attempt at a solution
    a) I got the correct answer but I don't understand why the 0.87 km/h [N] was used instead of the 2.0 km[W]
    t=5.9 hrs
    b) total velocity= √0.87^2+2^2
    I'm really not sure what I'm trying to look for??
  2. jcsd
  3. Oct 30, 2016 #2
    Your answer to Part A was correct because motion in the X direction is independent of motion in the Y direction.
    As the swimmer swims to the other side, you're given the swimmer's speed as she swims across. The current of the river doesn't affect the time it takes for the swimmer to reach the other side.

    For Part B, you want how far she's been taken down stream during the time it took for her to reach the other side, or delta X.
    Let me know if you have any other questions.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted