calculating percent error in a lab please help!! 1. The problem statement, all variables and given/known data I have to calculate an experimental value for g using values from my lab. I got -45.9 as my value, and now i have to calculate the percent error 2. Relevant equations a= g (m2 - m1/ m2+m1) was the equation i used actual-calculate/calculated x 100 3. The attempt at a solution Would I use negatives or not? 9.81- - 45.9 / - 45.9 x 100 = -121.4 % or 9.81-45.9 / - 45.9 x 100 = 78.6 % part b says derive the equation for a in the form a = F/m (f and m in terms of forces and messes in the atwood machine) but I have no idea what he is asking me to do thank you!