Hello Madams and Sirs. Newby here. I'm in the middle of engineering a new product for the percussion market which involves the use of a few magnets. Question is thus. What is the formula to determine the applied force of a given strength magnet or magnets over a given distance.? The apparatus i've designed is to hopefully be secured via magnets either side of a wooden plate..Now, i've determined the weights and applied forces the said apparatus will experience, but just need to calculate how much attracting force i'm going to need to stop it coming off under playing conditions, and to keep it from being to expensive to produce. I would rather not use Vecro or similar fixative. The approach is a wee bit unorthodox. But, i'm attempting something new. I knew I should of paid more attention in physics class, instead of drumming on the desk.! Thank you.