You'll experiment with sheet magnets of various areas, observing how many sheets of paper they can hold against a vertical surface. 

Select a 1 cm2 area, then click the Add Sheet button to increase the number of sheets. Record the maximum number of sheets that can be held.  Repeat for 4 and 9 cm2. Does a magnet with an area of 4  cm2 hold 4 times more sheets than a 1 cm2 magnet?  Can you explain why?