1. Not finding help here? Sign up for a free 30min 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!

Density question.

  1. Oct 30, 2011 #1

    lionely

    User Avatar

    1. A spring balance has a maximum reading of 10N and the length of the calibrated scale is 20cm. A rectangular metal block measuring 10cm by 3cm by 2cm is hung on the balance and stretches the spring by 15cm. Calculate
    i) the weight of the block;
    ii) the mass of the block;
    iii) the density of the metal from which the block is made.(Assume G 10m/s^2)



    3. The attempt at a solution

    I'm not sure how to attempt the question, but my friend tried to help me but he doesn't even know himself... I must do this question. :(
     
    lionely, Oct 30, 2011
  2. jcsd
    Phys.org - latest science and technology news stories on Phys.org
  3. Oct 30, 2011 #2

    sandy.bridge

    User Avatar

    It's a 20 cm scale with a maximum reading of 10 N. Break this 10 N value up over the entire scale. You can use this to determine how heavy the block is.
     
    sandy.bridge, Oct 30, 2011
  4. Oct 30, 2011 #3

    lionely

    User Avatar

    So 10N/20cm?? = 0.5?
     
    lionely, Oct 30, 2011
  5. Oct 30, 2011 #4

    sandy.bridge

    User Avatar

    Okay, 0.5N/cm. If the block causes a 15cm displacement , what would that be in terms of force?
     
    sandy.bridge, Oct 30, 2011
  6. Oct 30, 2011 #5

    lionely

    User Avatar

    Oh ummm 0.5N/cm x 15cm = umm 7.5N?
     
    lionely, Oct 30, 2011
  7. Oct 30, 2011 #6

    sandy.bridge

    User Avatar

    Yes, now how do you relate the mass of a substance to its weight?
     
    sandy.bridge, Oct 30, 2011
  8. Oct 30, 2011 #7

    lionely

    User Avatar

    Hmmm F=ma umm considering a(g) = 10m/s^2, 7.5N = m x 10

    m= 7.5/10= .75kg?
     
    lionely, Oct 30, 2011
  9. Oct 30, 2011 #8

    sandy.bridge

    User Avatar

    Okay, can you figure out the density now?
     
    sandy.bridge, Oct 30, 2011
  10. Oct 30, 2011 #9

    lionely

    User Avatar

    Yes density = mass/volume = .75kg/0.6m?
     
    lionely, Oct 30, 2011
  11. Oct 30, 2011 #10

    sandy.bridge

    User Avatar

    I would reconsider your volume component. Remember
    [tex]V=lwh[/tex]
     
    sandy.bridge, Oct 30, 2011
  12. Oct 30, 2011 #11

    lionely

    User Avatar

    but the components 10 x 3x2?
     
    lionely, Oct 30, 2011
  13. Oct 30, 2011 #12

    sandy.bridge

    User Avatar

    Not entirely sure what units your teacher wants you to be using, but yes that is the right idea. You may be required to give your answer in cubic meters rather than cubic centimeters, though.
     
    sandy.bridge, Oct 30, 2011
  14. Oct 30, 2011 #13

    lionely

    User Avatar

    lol i'm stupid I converted wrongly i converted the cubic centimetres as it was centimetres I divided by 100 when I should divided by like 10^6?
     
    lionely, Oct 30, 2011
  15. Oct 30, 2011 #14

    sandy.bridge

    User Avatar

    Here is an easy way to do it.

    V=(3/100 m)(2/100 m)(10/100 m)
     
    sandy.bridge, Oct 30, 2011
  16. Oct 30, 2011 #15

    lionely

    User Avatar

    Oh thank you, but I got it. I'll remember that way.
     
    lionely, Oct 30, 2011
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Density question.

  1. Density Question (Replies: 4)

  2. Density Question? (Replies: 1)

  3. Density Question (Replies: 4)

  4. Work density / heat density question (Replies: 1)

  5. Density question (Replies: 5)

Loading...