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!

Immedaite Help Is required

  1. Feb 11, 2010 #1
    Hello every one, I wish if you could help with this problem :

    b]1. The problem statement, all variables and given/known data[/b]

    Given the following informaiton for a paritculart watershed, determine the amount of the annual precipitaion recieved

    2. Relevant equations

    water shed area : 4530 m^2
    average flowrate : 39.6 m^3/second
    Average infiltration 9.2 * 10 ^ -7 m/s
    Evapo-transpirtaiton : 45 cm/year
    change is storage -23.9 cm/year

    3. The attempt at a solution

    I am sure that the formula to solve this is : change in storage = input - output + prec. - Evaportaion .

    However, I have some doubts :

    First, I assumed that the Evapo-transpirtaiton is the same as : Evaportaion so I am going to substitute it in the formula .

    Second, which is the major :
    The units - do we need to convert the units ?
    My idea is to convert all cm to m but then when prec.is found : how to know if m/year

    or m/s ?

    Hope hearing replying soon =)
  2. jcsd
  3. Feb 12, 2010 #2


    User Avatar

    Just transform all to a single unit. No matter what transformation you make if you have a single set of units the result will be right. And after you can transform the result in any unit system you want or anything that fits better, m/year maybe.


    m instead of any other lenght unit
    year instead of second .......as at such a surface area the second seems small.
  4. Feb 12, 2010 #3
    so, you're saying that I need to make all cm to m and all seconds to years.

    But the numbers will be sooo big because there are a really huge amount of seconds in one year ..

    So, is that ok ?
  5. Feb 12, 2010 #4


    User Avatar

    Staff: Mentor

    That's where the scientific notation (6.02x1023) comes in handy.
    Last edited by a moderator: Aug 13, 2013
  6. Feb 14, 2010 #5
    Ok, thnx I 'll try this >
  7. Feb 14, 2010 #6
    Borek you made me laugh :)
  8. Feb 14, 2010 #7
    But, what if I got powers with(-) sign ?
  9. Feb 15, 2010 #8


    User Avatar

    Staff: Mentor

    That's OK, that's part of the notation. Do you know what it means?
    Last edited by a moderator: Aug 13, 2013
  10. Feb 18, 2010 #9
    ya .. thnx alot
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Threads - Immedaite Help required Date
Lab Report Help -- total amount of CaCO3 in an unknown antacid tablet Jan 23, 2018
Help Naming Hydrocarbons Jan 6, 2018
Calculating amount of HCL required Aug 16, 2016