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!

Frictional Force

  1. Apr 8, 2007 #1
    Frictional Fore


    m=0.2kg
    h1=1.65m
    h2=0m
    v1=0m/s
    v2=4.02m/s


    [​IMG]

    Calculate the frictinal Force
     
    Last edited: Apr 8, 2007
  2. jcsd
  3. Apr 8, 2007 #2
    i might be able to help - but what does the 'h' stand for
     
  4. Apr 8, 2007 #3

    Doc Al

    User Avatar

    Staff: Mentor

    Well? What have you done so far?

    Hint: There are two ways to go about this: (1) you can calculate the acceleration using kinematics and use that to find the net force, or (2) you can use energy methods.
     
  5. Apr 8, 2007 #4
    Kinetic Energy1=0J
    Kinetic Energy1=2.1J
    Gravitational Potential Energy1 =2.3J
    Gravitational Potential Energy2 =0J
     
  6. Apr 8, 2007 #5
    how vcan i find acceleration i haven't time
     
  7. Apr 8, 2007 #6
    The net force is equal to mass*acceleration
     
  8. Apr 8, 2007 #7
    i know but how can i find net force and acceleration
     
  9. Apr 8, 2007 #8
    you need to use perpendicular and parallel components
     
  10. Apr 8, 2007 #9
    Kinetic Energy1=0J
    Kinetic Energy1=2.1J
    Gravitational Potential Energy1 =2.3J
    Gravitational Potential Energy2 =0J
     
  11. Apr 8, 2007 #10
    I havent done energy yet at school - I would have to use kinematics, sorry
     
  12. Apr 8, 2007 #11
    [tex]Given[/tex]
    [tex]m=0.2kg[/tex]
    [tex]\Delta d=0m[/tex]
    [tex]{v}_{1}=0m/s[/tex]
    [tex]{v}_{2}=3.96m/s[/tex]
    [tex]{h}_{1}=1.65m[/tex]
    [tex]{h}_{2}=0m[/tex]

    [tex]Required[/tex]

    [tex]{F}_{f}[/tex]

    [tex]Solution[/tex]

    [tex]v_{ave} = (v_1 + v_2)/2[/tex]
    [tex]v_{ave} = (0m/s + 4.02m/s)/2[/tex]
    [tex]v_{ave} = 2.01m/s[/tex]

    [tex]\Delta t = \Delta \vec d/\Delta v_{ave}[/tex]
    [tex]\Delta t = 2.52m/2.01m/s[/tex]
    [tex]\Delta t = 1.25s[/tex]

    [tex]\vec a = \Delta v / \Delta t[/tex]
    [tex]\vec a = (2.01m/s) / 1.25s[/tex]
    [tex]\vec a = 1.608m/s^2[/tex]



    [tex]{E}_{T}={m}g\Delta h[/tex]
    [tex]={0.2kg}*9.8N/kg*1.65m[/tex]
    [tex]{E}_{g}=3.234J[/tex]


    [tex]{E}_{k}=(1/2)m{v}_{ave}^2[/tex]
    [tex] =(1/2)0.2Kg(2.01m/s)^2[/tex]
    [tex]{E}_{k}=0.40J[/tex]

    [tex]{E}_{T}={E}_{k}+{W}_{f}[/tex]
    [tex]3.234J=0.40J+\vec F_{f}\Delta d[/tex]
    [tex]3.234J=0.40J+\vec F_{f}2.52m[/tex]
    [tex]\vec F_{f}=2.834J/2.52m[/tex]
    [tex]\vec F_{f}=1.112N[/tex]
     
    Last edited: Apr 8, 2007
  13. Apr 8, 2007 #12
    nexxxt?????????/
     
  14. Apr 8, 2007 #13

    Doc Al

    User Avatar

    Staff: Mentor

    You don't need time--you have distance and speed.
     
  15. Apr 8, 2007 #14
    i have height

    i have n't distance
     
  16. Apr 8, 2007 #15

    Doc Al

    User Avatar

    Staff: Mentor

    Hint: If there were no friction, the mechanical energy would be constant. The loss of mechanical energy equals the work done by friction. (I did not check your calculations, but don't round off until the last step. Two digits is not accurate enough.)
     
  17. Apr 8, 2007 #16
    syou mean distace is 1.65m
     
  18. Apr 8, 2007 #17

    Doc Al

    User Avatar

    Staff: Mentor

    Do you have the angle made by the ramp? (I can't read the writing on the diagram.)
     
  19. Apr 8, 2007 #18
    i have not angle
    only that

    m=0.2kg
    h1=1.65m
    h2=0m
    v1=0m/s
    v2=4.02m/s


    [​IMG]

    Calculate the frictinal Force
     
  20. Apr 8, 2007 #19

    Doc Al

    User Avatar

    Staff: Mentor

    If you don't have the distance over which the friction acts (or enough info to figure it out) I don't see how you can determine the friction force. (Sorry for not catching that earlier.)

    After all, if the ramp were 100 m long you'd need much less friction than if it were 1 m long.
     
  21. Apr 8, 2007 #20
    d=2.52m.........
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Frictional Force
  1. Frictional Forces (Replies: 1)

  2. Friction Force (Replies: 3)

  3. Frictional Force (Replies: 6)

  4. Friction and forces? (Replies: 6)

  5. Force and Friction (Replies: 4)

Loading...