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: Kinematics Question

  1. Oct 4, 2009 #1
    1. The problem statement, all variables and given/known data
    A police car stopped at a set of lights has a speeder pass it at 100 km/h. If the police car can accelerate at 3.6 m/s squared

    a) how long does it take to catch the speeder

    b) how far would the police car have to go before it catches the speeder?

    c) what would its speed be when it caught up with the car? Is this speed reasonable?

    2. Relevant equations

    not sure about these but:

    v2 = v1 + a(delta)t

    d = speed over time.

    3. The attempt at a solution

    At first I thought I just needed to calculate how long it would take for the police car to get to 100 km/h, but then I realized that the speeder is going 100km/h. I'm just really confused because there are two objects that you have to keep track of instead of just one. I have no clue where to start on this question.
  2. jcsd
  3. Oct 4, 2009 #2
    Since you know that you are trying to find the time taken for the police car to catch the other car, you know that when he does, their displacements are going to be the same. So if you get an equation for the displacement of each car, you can equate them to each other to find the time. So do you know a kinematic equation that relates displacement, initial velocity, acceleration and time?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook