Virtual Bridge Experiment

Experiment 1: How is the thickness of a bridge related to it's strength?

Pick a length. How many pennies does it take for a bridge to break of thickness 2 units? 3 units? 4 units? 5 units? ...
 
Determine a way to predict the number of pennies that will be required for any thickness.
 

Experiment 2: How is the length of a bridge related to it's strength?

Pick a thickness. How many pennies does it take for a bridge to break of length 2 inches? 3 inches? 4 inches? 5 inches? ...
 
Determine a way to predict the number of pennies that will be required for any length.
 

Challenge: Can you determine a formula to predict the number of pennies that will be required for any thickness or length?