Your browser can't run 1.0 Java applets, so here's a picture of the window the program brings up:

Applet by Fu-Kwun Hwang

Virtual Physics Laboratory

Instructions on how to use the animation below-
  • Click on Start to start the animation and Brake to stop the car.
  • The time delay is the time taken from the time that the red light is turned on to the time that you you click on the brake button. The time shown in the textfield is equal to the time delay plus the time required for the car to stop once the brake has been applied.
  • You can change the following parameters -
    • The Initial Speed of the car : The default value for the initial speed of the car is 72 km/h = 20 m/s. You may also select the units of speed.
    • The kinetic coefficient of friction of the tires on the road. The default value is 0.8
  • A series of dots are displayed with in the animation as the car moves from left to right. The height of these dots above the ground (i.e., their y coordinate) is proportional to the speed of the car. Notice that it is not a straight line after the brake turned on! Why?
  • Place your mouse over any of the aforementioned dots. The speed of the car at the time that it was at that location is shown in the textfield marked mouseXV.
  • Press Reset button to restart the applet.



Reaction time : the lapse of time between stimulation and the beginning of response.

    You are driving on the high way and listening to the music you like most.

    Suddenly, you see that the brake light of the car in front of you just came on.

    You try to hit the brake and slow down your car.

    But, there is a small time delay between the time that you first see the brake light of the car in front of you and the time that you step on the brake. This is your reaction time.

    During that period of time, your car is still moving at the same HIGH speed!

    What is minimum distance that you must maintain between front of your car and the rear of the car before yours if you do not want something VERY BAD happened?

    If both cars need the same distance to fully stopped (why is this relavant?), the minimum distance is

      ( the velocity of your car )* ( your reaction time )