GUN So I couldn't figure this problem on my physics final. Help?

Discussion in 'On Topic' started by xpinchx, Dec 14, 2007.

  1. xpinchx

    xpinchx hes got a nice cock, on the thin side but its stil

    Joined:
    Dec 18, 2003
    Messages:
    46,800
    Likes Received:
    0
    Location:
    East Lansing, MI
    It was tied in with some kinematics stuff but I couldn't figure it out for the life of me.

    Info given:
    Mass of a train (kg)
    Speed of train (km/h, convert to m/s)
    Brake is applied with a force (given in N)
    Brake is applied for time (s)

    Find the final velocity after braking for t seconds.

    It was literally the first question on the test. I tried almost everything I could think of. The first (and most logical) thing I tried was taking the force of the brakes and dividing by the mass of the train to get the acceleration, then just plugging that into a kinemeatics equation, Vx=Vox + a*t, but that didn't get me anything close to any of the multiple choice answers. :dunno:

    Any ideas?
     
    Last edited: Dec 14, 2007
  2. MTech

    MTech New Member

    Joined:
    Mar 3, 2007
    Messages:
    1,862
    Likes Received:
    0
    WTF does this have to do with WMD? :ugh:
     
  3. xpinchx

    xpinchx hes got a nice cock, on the thin side but its stil

    Joined:
    Dec 18, 2003
    Messages:
    46,800
    Likes Received:
    0
    Location:
    East Lansing, MI
    wrong forum my bad.
     
  4. xpinchx

    xpinchx hes got a nice cock, on the thin side but its stil

    Joined:
    Dec 18, 2003
    Messages:
    46,800
    Likes Received:
    0
    Location:
    East Lansing, MI
    Well, I was going to delete it but I think I might leave it since it obviously upset you so much.
     
  5. mattsb2000

    mattsb2000 OT Supporter

    Joined:
    Jun 15, 2003
    Messages:
    61,666
    Likes Received:
    1
    Location:
    San Bernardino, CA
    :rofl:
     
  6. MTech

    MTech New Member

    Joined:
    Mar 3, 2007
    Messages:
    1,862
    Likes Received:
    0
    03 w/ 33k posts should know better..


    [​IMG]
     
  7. mattsb2000

    mattsb2000 OT Supporter

    Joined:
    Jun 15, 2003
    Messages:
    61,666
    Likes Received:
    1
    Location:
    San Bernardino, CA
    How about no.
     
  8. MTech

    MTech New Member

    Joined:
    Mar 3, 2007
    Messages:
    1,862
    Likes Received:
    0
    [​IMG]
     
  9. xpinchx

    xpinchx hes got a nice cock, on the thin side but its stil

    Joined:
    Dec 18, 2003
    Messages:
    46,800
    Likes Received:
    0
    Location:
    East Lansing, MI
    :07: should know better.
     
  10. PanzerAce

    PanzerAce Active Member

    Joined:
    Feb 25, 2006
    Messages:
    14,502
    Likes Received:
    0
    Location:
    N37°18'37" W120°29'50"
    it stops when it hits the bottom after falling off the bridge that was blown the fuck up :o
     
  11. MTech

    MTech New Member

    Joined:
    Mar 3, 2007
    Messages:
    1,862
    Likes Received:
    0
  12. 2L Bunny

    2L Bunny "It's only a Rabbit"

    Joined:
    May 18, 2001
    Messages:
    1,673
    Likes Received:
    0
    Location:
    OR
    Fuck, I read your post and starting thinking of equations and started making a FBD in my head. Damn...I'm an engineer....
     
  13. SNDP

    SNDP New Member

    Joined:
    Nov 26, 2007
    Messages:
    788
    Likes Received:
    0
    Location:
    Zion
    plug all of the answers into the equation until one works out. I love algebra or physics tests with multiple choice answers. ONE of the answers is right, plug them in until one works!
     
  14. Clingman

    Clingman Clingman runs Bartertown.

    Joined:
    Apr 1, 2004
    Messages:
    2,731
    Likes Received:
    0
    Location:
    Thunderdome
    You have enough there to find v(t), velocity at any time. You were given the total time it takes to stop the train. The integral of velocity will give your displacement. You need to integrate v(t) from time 0 to time t.
     
  15. Clingman

    Clingman Clingman runs Bartertown.

    Joined:
    Apr 1, 2004
    Messages:
    2,731
    Likes Received:
    0
    Location:
    Thunderdome
    Don't say gun crew never did anything for you :)
     
  16. Keesh

    Keesh New Member

    Joined:
    Oct 26, 2003
    Messages:
    15,333
    Likes Received:
    0
    There is an elephant in the way.
     
  17. 01_Cruiser

    01_Cruiser An American Classic OT Supporter

    Joined:
    May 22, 2003
    Messages:
    45,895
    Likes Received:
    0
    Location:
    NC
    :rofl:
     
  18. xpinchx

    xpinchx hes got a nice cock, on the thin side but its stil

    Joined:
    Dec 18, 2003
    Messages:
    46,800
    Likes Received:
    0
    Location:
    East Lansing, MI
    I never really thought to apply calculus to physics. I'm in algebra-based so they never really showed us how to apply calculus to what we're learning. At least not in a straight-forward manner.
     
  19. [DWI]

    [DWI] Master of Nothing

    Joined:
    Aug 6, 2000
    Messages:
    21,936
    Likes Received:
    0
    Location:
    Maine
    The Ice Cream is melting.
     
  20. Wave

    Wave Carlos Spicy Weiner

    Joined:
    Mar 21, 2000
    Messages:
    3,524
    Likes Received:
    0
    Location:
    Seattle, WA
    I must be missing something... what exactly are you looking for. I don't see the question, just a bunch of info. :confused:
     
  21. xpinchx

    xpinchx hes got a nice cock, on the thin side but its stil

    Joined:
    Dec 18, 2003
    Messages:
    46,800
    Likes Received:
    0
    Location:
    East Lansing, MI
    lol, the final speed after braking for t seconds. My bad.
     
  22. Alphaeus

    Alphaeus New Member

    Joined:
    Oct 5, 2003
    Messages:
    12,101
    Likes Received:
    0
    Location:
    Chicago
    [​IMG]
     
  23. XR250rdr

    XR250rdr OT Supporter

    Joined:
    Mar 1, 2004
    Messages:
    24,479
    Likes Received:
    21
    Location:
    Ca
    F=ma <- F is brake force, m is train mass. Solve for a

    v(t) = vo + at <-substitute in initial velocity (vo), acceleration (a) (remember its negative), and braking time (t).
     
  24. XR250rdr

    XR250rdr OT Supporter

    Joined:
    Mar 1, 2004
    Messages:
    24,479
    Likes Received:
    21
    Location:
    Ca
    If they arent teaching it to you, dont worry about it now. You wont need calc to do any of the problems just yet.
     
  25. xpinchx

    xpinchx hes got a nice cock, on the thin side but its stil

    Joined:
    Dec 18, 2003
    Messages:
    46,800
    Likes Received:
    0
    Location:
    East Lansing, MI
    That's exactly what I tried to do, but it was a multiple choice question and none of them were even close to what I got. :dunno:
     

Share This Page