physics

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a stunt car driver testing the use of air bags drives a car at a constant speed of 25m/s for a total of 100 meters. he applies his brakes and accelerates uniformlu to a stop just as he reaches the wall 50 meters away. SKETCH THE A GRAPH SHOWING POSITION V.S TIME and VELOCITY v.s TIME
also how long does it take the car to travel the first 100 meters?

  • physics -

    first do the stopping problem
    d = Vi t + .5 a t^2
    d = 25 t + .5 a t^2
    50 = 25 t + .5 a t^2

    v = Vi + a t
    0 = 25 + at
    a t = -25
    a = -25/t
    combine 50 = 25 t - .5(25t)
    50 = .5 (25 t)
    t = 4 seconds to stop after applying brakes
    a = -25/4 while stopping
    Now do the problem
    for the first part
    x = 25 t until t = 2 where x = 50
    then x = 50 + 25(t-2) - (25/8) (t-2)^2
    until stopped at x = 100 and t = 6
    during deacceleration v = 25 -(25/4)(t-2)

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