Logger Pro can calculate and plot the position and velocity of the center of mass of a set of tracked objects in a video analysis project. For example, the motion of two carts on a track might be followed through a collision. While the motion of neither cart is uniform throughout the collision, in the absence of external forces the center of mass will move at constant speed.
To use this feature with a video showing the motion of several objects, first mark the position of one object through the video. Then return to the first marked frame, and add a new point series using Add Point Series from the Set Active Point button. Mark the positions of second object through the video. Repeat for additional objects as needed.
Now return to the Set Active Point button, and choose Add Center of Mass Series from the menu. This menu item appears only if there are two or more point series present.
The resulting dialog allows you to select or deselect a point series for use in the center of mass calculation, as well as to set the mass to be associated with each point series. You can set the mass units as well as the name of the Center of Mass series. The unit name and decimal place display are used only in this dialog at this time.
Once a Center of Mass series has been created, the location is plotted on the video for each frame, and the data table will display the X and Y position and velocity of the Center of Mass series.
These columns can be graphed and analyzed if desired.
Once a Center of Mass series has been created, it can be edited or deleted by selected the series in the Set Active Point menu.
Like other drawn points on the video, the Center of Mass markers takes their color from the column settings for the Y coordinate. To alter the color or point marker, use the column options for the Center of Mass Y.