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!

Find the maximum deflection of the spring

  1. Feb 23, 2013 #1
    1. The problem statement, all variables and given/known data
    The 3.8-kg collar is released from rest at A and slides down the inclined fixed rod in the vertical plane. The coefficient of kinetic friction is 0.51. Calculate (a) the velocity v of the collar as it strikes the spring and (b) the maximum deflection x of the spring.

    I have attached an image of the question.

    2. Relevant equations



    3. The attempt at a solution

    I was able to find the velocity of the collar with:

    U1 + K1 = U2 + K2 + F

    K1 and U2 are 0

    F is the friction force

    0.5mv2 = mgh1 - F

    Drawing a FBD of the collar shows that the Normal force (F = ukN):

    N = mgsin(27)

    0.5(3.8kg)v2 = (3.8kg)(9.81 m/s2)(0.57sin(63)) - (0.51)(0.57m)(3.8kg)(9.81m/s2)sin(27)

    Solving for v gives me:

    v = 2.7157

    I can't seem to find the displacement of the spring though.

    I realize that F = -kx and I need to find F to get x.

    Looking at the practice question (identical scenario but different numbers) led me to believe that the answer should be:

    F = mg - mgsin(27)

    x = sqrt[mg-ukmgsin(27)/2700]

    x = 103 mm
    But it says this isn't correct and I'm not sure where I'm making my mistake.

    Help is appreciated.
     

    Attached Files:

  2. jcsd
  3. Feb 23, 2013 #2

    TSny

    User Avatar
    Homework Helper
    Gold Member

    Note that force and energy have different dimensions, so they can't be added together.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook