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Homework Help: Spring Constants, Work, and Force

  1. Mar 21, 2013 #1
    1. The problem statement, all variables and given/known data
    Suppose for some unexplained reason you are skateboarding and wanted to use a spring to launch you off a ramp. Assuming you have a mass of 70 kg, if the spring has a spring constant k = 625N/m and is compresed 5m.
    1.If the ramp has a 60° and is 10m long, will you make it off the ramp?
    2. How high will you go?
    3. How fast will it be going when it enters the ramp (ignore friction)?

    2. Relevant equations
    1/2mv(intial)squared + mgh(initial) + 1/2k(initial)xsquared = 1/2mv(final)squared + mgh(final) +1/2k(final)xsquared

    3. The attempt at a solution
    To get the first answer, the second question has to be answered. I got 1/2k(intial)xsqured = mgh(final). 1/2(625)(5)squared = 70(9.8)h(final). 7812.5 = 686h(final). 11.4m=h(final).
    After this, I have no clue how to get the first and third question.

    Thanks ahead of time.
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Mar 21, 2013 #2
    To answer #1, you need to determine whether the result in #2 is higher than the end of the ramp.

    In #3, I do not understand what "it" is.
  4. Mar 21, 2013 #3
    The it in #3 is the skateboard... I think.

    And the answer to #2 is 11.4m=h(finial). But I don't understand how to get the answer to number one.
  5. Mar 22, 2013 #4
    I think I have the answers. Thanks for the help.
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