My question concerns the y-intercept of the force vs. acceleration graph. When I plotted my data, the regression line had an intercept that was not 0. What does this signify? I know that the intercept is the amount of force when the acceleration is 0 m/s^2. Shouldn't it be 0 N at 0 m/s^2? Does this mean there was a source of force that I neglected to take account for while recording the values for the graph? Thanks.