1. Not finding help here? Sign up for a free 30min 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!

Incline plane question

  1. Jul 13, 2008 #1
    1. The problem statement, all variables and given/known data

    Starting from rest, a cyclist coasts down the starting ramp at a professional biking track. If the ramp has the minimum legal dimensions(1.5 m high and 12m lomg) find
    a) the acceleration of the cyclist ignoring friction

    b) the acceleration of the cyclist if all sources of friction yield an effective coefficient of friction = .11

    c)time taken to reach the bottom of the ramp, if friction acts as in (b)

    2. Relevant equations

    My concern is the part a.
    V1= 0
    v2= ?
    a=?
    m=?
    d=12m

    I cant use Newton's 2nd law to find the a because the mass is not given nor the force.
    I looked at all kinematic equation and none of them works as well...so how do i approach solving this problem?
     
  2. jcsd
  3. Jul 13, 2008 #2
    The mass does not matter here.... It may get cancelled in the equations itself.
    Also try and upload a figure of the problem.
     
  4. Jul 13, 2008 #3
    no figure was given in the question
     
  5. Jul 13, 2008 #4

    LowlyPion

    User Avatar
    Homework Helper

    You know the height of the starting point 1.5m and you know the length of the starting ramp 12m and you know the value of gravity. 9.8m/s^2. You should be able to develop what the value of the constant acceleration is on the cycle shouldn't you?
     
  6. Jul 13, 2008 #5
    i dont get it...how?
     
  7. Jul 13, 2008 #6
    Firstly the dimensions of the ramp give the angle of inclination of the ramp. If the height is [tex]\var H[/tex] and the length of the ramp be [tex]\var L[/tex], then [tex]tan\vartheta=\frac{\var H}{\var L}[/tex]
    The particle model can be used here.
    Let the mass of the particle be [tex]\var m[/tex]
    Then observing the equilibrium perpendicular to the ramp,
    [tex]\var N = \var mg cos \vartheta[/tex]
    and along the ramp
    [tex]mg sin \theta - \mu mg cos\theta = ma[/tex]
    [tex]a=g sin \theta - \mu g cos\theta [/tex]

    which is independent of [tex]m[/tex]
     
  8. Jul 13, 2008 #7
    thank you. is the answer
    1.2 m/s^2 for part a and .13m/s^2 in part b?
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Incline plane question
Loading...