another weigh to go !

Two scales are placed some distance D apart. A rigid board is placed across the two scales, and both scales are adjusted to read zero. Enter the value of the mass to be placed on the board. Slide the mass along the board. Can you explain the readings? What questions could/would you ask your students based on this applet?
Can you devise a way to weigh a 350 lb. motorcycle using a bathroom scale whose upper limit is 200 lb ?