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!

Homework Help: Spring - which one is correct?

  1. Dec 28, 2009 #1
    1. The problem statement, all variables and given/known data
    mass of the body=m

    Horizontally, the spring is deflected from its equilibrium position and then released, oscillated with a frequency f. Then, the same spring and the same body are suspended vertically, as in figure.

    Which one is correct?

    A) The frequency of movement of the spring, when the body is suspended vertically, doubled.

    B) The frequency of movement of the spring, when the body is suspended vertically, reduced to half.

    C) The frequency of movement of the spring, when the body is suspended vertically, remains the same.

    D) The frequency of movement of the spring, when the body is suspended vertically, is not related to the period of the movement, when the spring oscillates horizontally.

    2. Relevant equations



    3. The attempt at a solution

    I think is C) but I think that D) is also correct. Please help me
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     

    Attached Files:

  2. jcsd
  3. Dec 28, 2009 #2

    Doc Al

    User Avatar

    Staff: Mentor

    Re: Spring

    Describe how you came to that conclusion.
     
  4. Dec 28, 2009 #3
    Re: Spring

    I think is C) because the frequency is a characteristic of the oscillator.

    I think that D) is also correct because we change the position of oscillator and in the second case there are 2 forces: grav force and elastic force, in the first case there is only elastic force.
     
  5. Dec 28, 2009 #4

    Doc Al

    User Avatar

    Staff: Mentor

    Re: Spring

    It's true that when suspended vertically there are two forces to consider, but it still turns out that the frequency depends only on the ratio of k/m.

    How does period relate to frequency?
     
  6. Dec 28, 2009 #5
    Re: Spring

    f= 1/T

    so is C) ?
     
  7. Dec 28, 2009 #6

    Doc Al

    User Avatar

    Staff: Mentor

    Re: Spring

    Right.
    Yes, C is correct. D doesn't really make sense, since if the frequency is unchanged the period must also be unchanged.
     
  8. Dec 28, 2009 #7
    Re: Spring

    so the in spite of in 2nd case there are 2 forces acting, that doesn't change anything, right?
     
  9. Dec 28, 2009 #8

    Doc Al

    User Avatar

    Staff: Mentor

    Re: Spring

    What changes is the length of the spring when the system is at its equilibrium point. In the horizontal case, the equilibrium position is when the spring is unstretched; but when vertical, the spring is stretched at equilibrium (by an amount = mg/k).

    But that doesn't affect the choice of answer.
     
  10. Dec 28, 2009 #9
    Re: Spring

    oh ok, now I understand

    many thanks, really!
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook