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The maximum deceleration of a car

  1. Jan 24, 2010 #1
    The maximum deceleration of a car....

    1. The problem statement, all variables and given/known data
    The maximum deceleration of a car on a dry road is about 8.0 m/s^2


    3. The attempt at a solution
    A)
    If two cars are moving head-on toward each other at 88 km/h (55 mi/h), and their drivers apply their brakes when they are 85 m apart, will they collide?
    Answer: No


    B)
    How far apart will they be when they stop?
    Answer: 10m


    C) HELP Drawing the graph and points

    On the same graph, plot distance versus time for both cars.
    Assume x = 0 is the midpoint between the cars and t = 0 when the brakes are applied. Label the position versus time plot of the car with the positive velocity as x_1(t).
    http://img684.imageshack.us/img684/6803/94527989.png [Broken]
     
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Jan 24, 2010 #2
    Re: The maximum deceleration of a car....

    if x = 0 is the midpoint, car 1 is at x = -85/2 and car 2 is at 85/2 initially.

    x(t) = 1/2 a t^2 + v * t + x(i)
    so
    x_1(t) = 1/2 (-8) * t^2 + 88000/3600 * t - 85/2
    x_2(t) = 1/2 8 t^2 - 88000/3600 * t + 85/2
    Notice that car 2's velocity is positive (to the right) and its acceleration is negative(to the left). The reverse is true for car 2.
     
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