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: Mass of a paper clip question

  1. Jan 2, 2010 #1
    1. The problem statement, all variables and given/known data

    the mass of a paper clip is approximately?

    2. Relevant equations

    it is mutiple choice but i dont know if there an equation for it

    the mass of a paper clip is apporoximately?

    1) 1 x 10 exponenet(6) kg
    2) 1 x 10 exponenet(3) kg
    3) 1 x 10 exponenent(-3) kg
    4) 1 x 10 exponenent(-6) kg

    3. The attempt at a solution

    i have no idea how to do this problem ...
  2. jcsd
  3. Jan 2, 2010 #2


    User Avatar
    Gold Member

    There is no formula. Three of the options are ridiculous.

    The question is designed to see if you understand
    a] exponents,
    b] how to ballpark, and
    (possibly most important)
    c] how to understand a problem, rather than just being a calculating machine.
  4. Jan 2, 2010 #3
    Steel weighs about 490#/cu.ft so estimate/calculate the volume of a paper clip and go from there.
  5. Jan 2, 2010 #4
    Maybe you have played around with masses in a lab? Or you have passed around a 1 kg mass? A 100 gram mass (0.100 kg)? I think your teacher may have two or three things in mind.

    1. Do you have some feel for what a kilogram is? Maybe like you have a feel for about how long a foot is or a meter. Or maybe you can estimate how much of a pound a pea weighs.

    2. Do you understand scientific notation?
  6. Jan 2, 2010 #5
    maybe try to think about it in terms of grams
    it definitely has a negative exponent
    i think this one is more of a common sense question....
  7. Jan 2, 2010 #6


    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    If you must, try converting from kg to pounds or ounces, if you are more familiar with those units.

    As a reference, find a package of food, any type of food, which lists the mass on the package. Is a paper clip heavier or lighter than this? That should help eliminate 2 of the answers.
  8. Jan 2, 2010 #7
    Go to Staples or Office Max. Get a box of 100 paper clips. Weight it on a letter scale. Divide by 100.
  9. Jan 2, 2010 #8


    User Avatar
    Gold Member

    Just for a ballpark estimate, is a paper clip lighter than a penny? What is the mass of a penny? If you know how to handle exponents, the answer should be evident quickly.
  10. Jan 2, 2010 #9


    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    The point of this homework problem is not to weigh a paper clip, it is to use some common sense.
  11. Jan 2, 2010 #10
    The problem can be common sense is not common when one has no idea what a kilogram is. We can be sure the poster is not a drug dealer, in the U.S. anyways. Which is a good thing.
  12. Jan 2, 2010 #11


    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    The point is to get an idea what a kilogram is. If one doesn't know that, at least use the conversion to pounds. Going out and weighing to get the mass of a paper clip defeats the purpose.
  13. Jan 2, 2010 #12
    Ok, well first approximate, do you know what a kg is equal to? about 4 apples, now consider a small paper clip, it is very small compared to those apples, a tenth? a thousandth? a millionth? well you are in luck because it is multiple choice, so it is most likely 1EE-3

    If you don't know scientific notation (which you should, it will come up again) the -3 means the total number of digits. So 1EE-3 = .003th of a kg or 1g, 1g ~ a paper clip

    Good estimation is a valuable tool in science and IRL, the important thing is not the detail (3 or 4EE but the exponent, EE3, and EE6 is a big difference, you should be able to pick a reasonable answer)
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook