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

Basic Control Buttons

There are four basic control buttons. They are, from left to right:

Rewind. Resets the simulation to the starting point with the previously chosen values for the system parameters. After clicking Replay, click Play to restart the motion.

/ Play/Pause. Clicking starts the motion.

After Play has been clicked, the button will change into the Pause button . Click it if you want to take a 'snapshot' of the motion at a given instant. To resume the motion, click Play once more.

Step. Lets you step through the motion in equal time steps. The step size can be adjusted with the Time Step slider. See Point 6. In the Incremental mode (see Point 7), one must Step through the motion. Continuous Play is disabled.

Reset. Resets the applet to its default setting.

Adjustments in the system parameters can only be made after first clicking REPLAY or RESET.



Data



The Data box lists the following data, as illustrated in the preceding image.

Top section. Constants of the motion and initial values.

• d: initial phase angle; equal to q(0) (see below)
• a_tan(0): absolute value of the tangential component of the acceleration of the mass point at t = 0
• KE(0): absolute value of the kinetic energy of the mass point at t = 0

Note. The phase angle d can be chosen before starting the motion by dragging the mass point in its circular orbit.

Bottom section. Values of time-dependent quantities at time t.

• t: time elapsed since the beginning of the motion
• q(t): phase angle of mass point at time t; q(0) = d
• w(t): angular velocity of mass point at time t
• v(t): "circle velocity" of the mass point at time t; the circle velocity is a scalar quantity that can take on both positive and negative values; it is positive for counter-clockwise motion and negative for clockwise motion; its absolute value is equal to the speed of the mass point
• F_tan(t): absolute value of the tangential component of the net force acting on the mass point at time t
• F_rad(t): absolute value of the radial component of the net force acting on the mass point at time t
• W: net work done on the mass point between t = 0 and time t
• KE(t): absolute value of the kinetic energy of the mass point at time t



Vector



The Vectors toggle button lets you display/hide the Vector Panel illustrated above. Selecting a vector in this panel will cause that vector to be displayed. In the panel illustrated, the velocity of the mass point and the net force acting on the mass point and the components of the net force are selected. The corresponding vectors are shown in the image at the top of this Help document.

The following items are available in the panel:

• position: position vector of mass point; shown in cyan
• velocity: velocity vector of mass point, drawn with its tail end at the mass point; shown in magenta
• acceleration: acceleration vector of mass point, drawn with its tail end at the origin; shown in orange
• acc. comps.: radial and tangential acceleration component vectors, drawn with their tail ends at the origin; shown in pale orange
• force: net force acting on mass point; shown in blue
• force components: radial and tangential component vectors of the net force; shown in pale blue



Sliders

There are eight sliders in all, arranged in two rows of four each. Clicking on a slider to the left or right of the slider tab allows fine adjustment of the slider setting.

Clicking on the Input Dialog button of a slider will open a dialog for entering an exact value for the slider setting. The dialog for the r-slider is illustrated below. The range in which values can be entered, from 0.10 m to 0.30 m in this case, is indicated above the data entry field.



First Row

• 
  lets you set the radius r of the circle on which the mass point is moving between 0.10 m and 0.30 m
  
• 
  lets you set the initial angular velocity w(0) between 0.50 rad/s and 2.00 rad/s
  
• 
  lets you set the initial circle velocity v(0) of the mass point in the range from r×w(0)_min to r×w(0)_max; thus, setting the r-slider to a different value will affect the range of the v(0)-slider; for an explanation of the term "circle velocity" see under Point 2, "Data"
  
• 
  lets you set the size of the time step Dt by which the Step button advances the motion between 0.01 s and 1.00 s




Second Row

• 
  lets you set the mass m of the mass point between 0.50 kg and 2.00 kg; the width of the dot representing the mass point increases as the mass value increases
  
• 
  lets you set the initial angular acceleration a(0) between -0.50 rad/s² and 0.50 rad/s²
  
• 
  lets you set the initial rate of change of the circle velocity dv/dt(0) between r×a(0)_min to r×a(0)_max; thus, setting the r-slider to a different value will affect the range of the dv/dt (0)-slider; for an explanation of the term "circle velocity" see under Point 2, "Data"
  
• 
  lets you set the size of the scale factor for displaying vectors and the energy column between 1 and 20; the different items will be affected as follows:
  
  position - no change
  velocity - proportional to scale factor
  acceleration - proportional to square of scale factor
  force - proportional to square of scale factor
  kinetic energy bar - proportional to scale factor
  






Kinetic Energy Bar

The red bar in the lower right-corner of the applet represents the kinetic energy of the mass point.

The height of the bar is proportional to the scale factor set by the Zoom slider. The seting of the Zoom slider also affects the lengths of the velocity, acceleration, and force vectors.