Performance data and FOM calculations at the contest will be tabulated in standard form. An example of results for five hypothetical students is shown in Table 1. You may want to do your own calculations from the data, and make sure that you get the same FOMs as those in the table.
If a vehicle carries no pennies, its FOM will be zero no matter how fast to goes. On the other hand, for loads over some maximum number of pennies, say Pmax, the vehicle won't move at all. Its FOM will also be zero. It stands to reason that for some number of pennies (P) between zero and Pmax, the vehicle's FOM will be as high as possible.
So, having first built a vehicle, you then find the number of pennies which gives the highest FOM. You can do this by loading the vehicle with different numbers of pennies, and determining the FOM for each case by actual tests. You might get results like those shown in Table 2.
It may also be very helpful to make a graph of the data, showing FOM vs. number of Pennies.
This curve shows the FOM is greatest for loading around 20 pennies (mathematically, a maximum). So you'd do best with a loading of about 20 pennies. Since the graph is fairly flat near the maximum a few pennies more or less won't make much difference to the FOM. (This would be good - you don't want FOM to drop off sharply if a vehicle has a few passengers more or less than the ideal number.)
Every design should have a curve generally like this. Adding more magnets to your design might shift the position of the maximum FOM to more pennies, since you could support more of them. However, the value of the FOM could increase or decrease, depending on how well the vehicle drive could handle the extra load, the fact that increasing the number of magnets increases cost, etc.
So one way to start is to build a car which at least goes fast empty, and then determine the number of pennies to add (and the way to add them) to get the greatest FOM. Then test to see if fiddling with the number of magnets, car shape, etc. improve things.
P.O. Box 5000
Upton, NY 11973-5000