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!

Ice pressed against a spring

  1. May 25, 2009 #1
    1. The problem statement, all variables and given/known data

    A 49 g ice cube can slide without friction up and down a 31° slope. The ice cube is pressed against a spring at the bottom of the slope, compressing the spring 11.9 cm. The spring constant is 25 N/m. When the ice cube is released, what distance will it travel up the slope before reversing direction?

    2. Relevant equations
    Pi=Pf
    U=mgx, kx^2/2
    K=mv^2/2


    3. The attempt at a solution

    Initially U=k*x^2/2
    then at the end U=mgLsin31
    so then i combined the 2 equations and solve for L and got L=(k*x^2)/(2*.049*9.8*sin(31))
    it is saying its wrong....what am i doing wrong?
     
  2. jcsd
  3. May 25, 2009 #2

    Doc Al

    User Avatar

    Staff: Mentor

    Looks OK to me, assuming the distance is measured from the compressed position.
     
  4. May 25, 2009 #3
    Yeah that is right if you are considering from compressed pos. If it is from relaxed position, you might have to subtract 0.119. Is the answer 0.597m?
     
  5. May 25, 2009 #4
    yeah thas my anwser but its wrong.
     
  6. May 25, 2009 #5
    I tried both .7157 and when you subtract .597 and they both are wrong.
     
    Last edited: May 26, 2009
  7. May 26, 2009 #6
    bump..... I still dont know what I am doing wrong
     
  8. May 26, 2009 #7
    I have one try left!?! FML
     
  9. May 26, 2009 #8
    here is a copy of my work....

    Physics13.jpg

    Ui=(delta x^2)*k/2
    Uf=mgL

    solved for L= (delta x^2)*k/2mg
     
  10. May 26, 2009 #9

    Doc Al

    User Avatar

    Staff: Mentor

    As I said earlier, there's nothing wrong with your work. But online systems can be flaky. Since they gave the compression in units of cm, perhaps that's the units they want.

    Did you post the entire problem word for word exactly as it was given?
     
  11. May 26, 2009 #10

    Doc Al

    User Avatar

    Staff: Mentor

    For some reason you chose to find the vertical distance instead of the distance up the slope. I'd say your first post was correct.
     
  12. May 26, 2009 #11
    o ok I am almost positive here ill copy and paste it again......

    A 49 g ice cube can slide without friction up and down a 31° slope. The ice cube is pressed against a spring at the bottom of the slope, compressing the spring 11.9 cm. The spring constant is 25 N/m. When the ice cube is released, what distance will it travel up the slope before reversing direction?
     
  13. May 27, 2009 #12

    tiny-tim

    User Avatar
    Science Advisor
    Homework Helper

    Hi talaroue! :smile:

    (try using the X2 tag just above the Reply box :wink:)

    You need sin31º times (x + .119),

    and (assuming the ice stays on the spring) you need kx2 - k(.119)2 :wink:
     
  14. Jun 1, 2009 #13
    he didnt have his C++ language right, aka he forgot to incorporate the degrees into the anweser. Thanks eveyrone
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Ice pressed against a spring
Loading...