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PE, springs, energy

  1. Oct 20, 2009 #1
    1. The problem statement, all variables and given/known data

    A horizontal k=200N/m spring is compressed 80cm. A 10kg mass is palced at the of of the spring on a u(mew)=0.15 surface. The mass leaves the spring at the equilibrium (x=0) point with 3.23m/s. Find the total distance (starting from rest) travelled by the mass. (Answer= 4.35)

    yea i got my other homework questions but this one confused me. The solution is probably simple, but i have the tendency to overthink. Thank you for the help.

    2. Relevant equations

    PEs -umg(0.8) = KE

    3. The attempt at a solution

    1/2(200*x2) - (0.15*10*9.8*x)= 1/2 (10*v2)

    then i used the quadratic formula to find x, but i got like 0.76 i think.
  2. jcsd
  3. Oct 20, 2009 #2
    There is no need to consider the elastic potential energy; the question already tells you that the mass leaves the spring with a certain velocity, hence you can safely ignore the spring from then on.
  4. Oct 20, 2009 #3
    Yeah, start with when the mass leaves the spring. There is no need to take the spring in to consideration. It is just there to confuse you. When it comes to these problems, it's best not to over think them other wise you can get overwhelmed easily if you're just starting out. Spend time reading the problem rather than solving. Good Luck.
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