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: Sports Car Acceleration Question

  1. Jan 14, 2010 #1
    1. The problem statement, all variables and given/known data
    A sports car moving at constant speed travels 110m in 5.0s. If it then brakes and comes to a stop in 4.0s. what is its acceleration in m/s^2? Express the answer in terms of "g's." where 1.00 g = 9.80 m/s^2.


    2. Relevant equations
    I thought about using the equation a=v/t

    3. The attempt at a solution
    So I tried it sort of I am just sort of lost I am not really sure how to start....
     
  2. jcsd
  3. Jan 14, 2010 #2

    rock.freak667

    User Avatar
    Homework Helper

    You need to use the kinematic equations

    v=u+at

    v2=u2+2as

    s=ut+1/2at2


    Which one do you think you will have to use?
     
  4. Jan 14, 2010 #3
    What does the u stand for, that's not in my book?
     
  5. Jan 14, 2010 #4
    The car initially had a velocity of 110m/5s (22m/s) and came to a stop (0m/s) in 4.0s. The acceleration is the change in velocity over a time interval.
     
  6. Jan 14, 2010 #5
    So would we use the v=u+at since I have the 4.0s and the 22m/s? but what would go in for the u?
     
  7. Jan 14, 2010 #6
    u is initial velocity and v is final velocity.
     
  8. Jan 14, 2010 #7
    Okay I figured it out thanks so much the answer was -5.5 m/s^2 and then in g's it was -0.56 g's
     
  9. Jan 14, 2010 #8
    take u (initial speed) = 110 / 5 = 22m/s
    v = 0
    t = 4

    v = u + at
    0 = 22 + 4a
    4a = -22
    a = -5.5m/s^2
    a = (-5.5/9.8)g = -0.56g
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook