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: Physics 20 - Word Problems

  1. Sep 11, 2010 #1
    1. The problem statement, all variables and given/known data

    If a plane can travel 2.00 x 10^3 km in 3.00 hours, what is its velocity in m/s?


    2. Relevant equations



    3. The attempt at a solution

    V =
    d = 2.00 x 10^3 km
    t = 3.00h

    V = 2.00 x 10^3 km / 3.00h

    V = 2000km / 3.00h

    V = 666.67km/h

    666.67 kilometers = 666 670 meters - 666.67 hours = 2 400 012 seconds
    I'm not sure what to do at this step changing it to m/s

    V = ?m/s
     
  2. jcsd
  3. Sep 11, 2010 #2

    Dale

    Staff: Mentor

    When you are converting between different units remember that you can always multiply by factors of 1. E.g.

    [tex]\frac{1 min}{60 s}=1[/tex]

    If you pick your factors of 1 correctly you can get the units you don't want to cancel out and just leave the units you do want. E.g.

    [tex]120 s = 120 s \; 1 = 120 s \frac{1 min}{60 s} = 2 min[/tex]

    Notice how the s on top in the original units cancels out the s on bottom from the factor of 1, leaving only min from the factor of 1.
     
  4. Sep 11, 2010 #3
    I still don't understand.Are you converting into minutes? I converted into minutes which is 160minutes, do I take my m/160minutes to get my final answer of m/s?
     
  5. Sep 11, 2010 #4

    Dale

    Staff: Mentor

    You have km/h and you want m/s so you need a factor which gives you m on top and cancels out the km, and you need another factor which gives you s on top and cancels out the h. Can you figure out what those factors are?
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook