ATRACTOR

The applet consists of what we call the viewing area (with a gray background) and menus with buttons, text boxes and value control bars (with a blue background). However, it is worth noting that, as we will see later, in some cases, it is possible to also enter data directly in the display area.

Click on the image where you have questions.

Note: The following figures are non-manipulable images. In the figures marked with , if you hover the mouse over them you will see an animation.

The display zone is divided into five areas:

• in the area on the left is represented a pendulum formed by a ball of mass m subject to friction and the action of gravity, respectively values q, g and suspended by a string of length L. It is also assumed that the string has a resistance to stretching with value r. Drag the ball with the mouse to the desired starting position;

• in the central area there is a representation of the potential, kinetic and total energies of the pendulum at each instant.

  Dragging the mouse in this area vertically allows you to zoom;

• in the area on the right are represented (from top to bottom, respectively):
  • the graph of energy as a function of time;
  • the graph of the ball's height as a function of time;
  • the graph of the function x(t) where x(t) is the point on the plane corresponding to the position of the ball at time t (note that, in this graph, the coordinate axis corresponding to the independent variable t is precisely the axis of symmetry of the cylinder, but, unlike what happens in the rigid pendulum, here the graph is not necessarily contained in the cylindrical surface).

The initial parameters of the pendulum can be modified:

• in the case of the value of the initial angle between the pendulum and the vertical direction,
  • directly in the text box ,
  • dragging the pendulum ball;

• in the case of the initial speed value, directly in the text box ;

• in the case of length (L), mass (m), friction (q) and gravity (g) values,
  • entering the values in the text boxes;

  

  • dragging the control bars.

  

(Note that the string resistance (r) can only be changed with the control bar).

Once these values have been chosen, click on the button , to see the simulation of the pendulum movement.

The menu has the following options:

• : to reset the time value (t = 0);
• : to return to the initial configuration.

The following options, when selected, allow you to see:

• 
  • the velocity vector (in yellow) of the pendulum at each moment;
• 
  • forces acting on the pendulum (without friction) at each moment
    • centrifugal force () ;
    • weight () :
      • radial component () ;
      • tangential component () ;
    • sum of external radial and centrifugal forces;
    • symmetric of the previous vector (=bar reaction force).

In the three areas on the right side of the applet, try clicking on them with the right mouse button: you get a menu with other options for manipulating objects.

Among the options, it allows you to have a resizable window of the area where you clicked - for more information, click here.

The flag, at the top of the applet, indicates the language used. If you wish, click on it and select another language:

By clicking , you can choose between:

• : access this instruction page;
• : accesses information about the applet version*.