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!

One-Dimensional Kinematics problem

  1. Jun 23, 2005 #1
    Hi, i have some questions for the following problems.

    A car accelerate at -1.9 m/s2. Traveling at a constant velocity of 32 m/s, this car comes up behind a car traveling at a constant velocity of11 m/s.

    a) How close to the slower car can the driver of the faster car come before applying his brakes and still avoid a collision?

    b) At what time does the inevitable collision of the two cars occur?

    c) How far beyond its position at t = 0 does the slower car get before it is hit?

    so the |a1| = 1.9 m/s2
    v1 = 32 m/s
    v2 = 11 m/s.

    Since it accelerates in a negative direction then it is deccelerating at a constant rate. For every second the velocity with decrease by 1.9 until it crashes with the second car with has a constant velocity. Now I dont understand what the question is asking for part a)

    Can anyone help? thanks
  2. jcsd
  3. Jun 23, 2005 #2


    User Avatar
    Science Advisor
    Homework Helper

    Write the equations of motion for each car and then impose the conditions that fulfiled for the crash to happen.

  4. Jun 24, 2005 #3
    hi thanks for the reply.
    I found that the two equations for the position.

    X1 = V1t + .5 at^2
    X2 = D + V2t

    If i set these two equal, I should find the point of collision but there are two variables and they dont give me D or T. If they have given me D then the problem will be alot easier.

    On the first problem, I want to find the D but they did not provide me with a time.
  5. Jun 24, 2005 #4
    Try using the velocity equation for car 1 to find t.
  6. Jun 25, 2005 #5
    Better yet, use concept of relative velocity and relative acceleration. Set the final relative position at 0 and solve for initial position.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: One-Dimensional Kinematics problem