Part of this is a desire for precision - if I say "the acceleration due to gravity is 9.81 m/s\(^2\)", I know exactly how precise that number is (typically we assume the uncertainty is in the last dec...Part of this is a desire for precision - if I say "the acceleration due to gravity is 9.81 m/s\(^2\)", I know exactly how precise that number is (typically we assume the uncertainty is in the last decimal point, so that implies \( \pm 0.01~m/s^2\) on that nunber).
