Help - Rolling Motion

The Applet shows the motion of a point on a rolling spool

Rolling Motion Help Map

Click on a number to view the explanation of the corresponding item.



  1. Basic Control Buttons
  2. There are six basic control buttons. They are, from left to right:

    Rewind Rewind. Resets the simulation to the initial position with the previously chosen initial values. If the path is displayed, Rewind will allow you to compare paths traversed under different conditions, e.g., different initial velocities.

    After clicking Rewind, click Play to restart the motion.

    Step Back Step. Lets you step through the motion in equal time steps going from right to left.


    Reverse Play Reverse/Pause. Starts the motion in reverse direction, i.e., from right to left.

    After REVERSE has been clicked, the button will change into the PAUSE button Pause.

    Clicking PAUSE will freeze the motion. To resume the reverse motion, click REVERSE once more.

    Play Play/Pause. Starts the motion in forward direction, i.e., from left to right.

    After Play has been clicked, the button will change into the Pause button Pause.

    Clicking Pause will freeze the motion. To resume the motion, click Play once more.

    Step Step. Lets you step through the motion in equal time steps in the forward direction, i.e., from left to right.

    Reset Reset. Resets the applet to its default setting.

    Adjustments in the initial conditions can only be made after first clicking REWIND or RESET.

    Back to Top

  3. Trace Trace
  4. This toggle button displays/hides the path of the moving point.

    Back to Top

  5. Vectors Vectors Button
  6. The Vectors toggle button displays/hides the vector panel shown below.

    Vector Panel

    Check the checkbox for a vector to display that vector. Three velocity vectors can be displayed:

    When the motion is paused, the velocity vector vector u can be dragged. By placing it so that its tail end is at the tip of the velocity vector v', you can demonstrate that the three velocities satisfy the Galilean velocity addition theorem: vector v = vector v' + vector u.

    Back to Top

  7. Data Data Button.
  8. The Data toggle button displays/hides the two data boxes illustrated below. The two boxes can be dragged separately. The box on the left displays quantities that are constant during the motion and the elapsed time. The box on the right displays the coordinates of the revolving point in two frames of reference and the coordinates of the center of the spool.

    Data Boxes

    Left-hand column:


    Right-hand column:

    Back to Top

  9. Sliders
  10. Sliders

    There are three sliders in all. They are described below, in the order from top left to bottom right.

    You can adjust a slider setting either by dragging the slider tab or by entering an exact value in the slider input dialog.

    To enter an exact value, click on the Input Dialog button Input Dialog Button of the slider to open the dialog. The dialog for the Angular Speed slider is illustrated below. The range in which values can be entered, from 0 to 2.00 rad/s in this case, is indicated above the data entry field.

    Input Dialog Field

    Clicking on a slider to the left or right of the slider tab allows fine adjustment of the slider setting.

    Back to Top

  11. Support Setting Top or Bottom
  12. Top: select this radio button to have the spool's inner cylinder supported from above, as in the following snapshot.

    Support on Top

    Bottom: select this radio button to have the spool's inner cylinder supported from below, as in the following snapshot. This is the default setting.

    Support at Bottom

Back to Top