The period of oscillation of a simple pendulum is given by where l is about 100 cm and is known to have 1mm accuracy. The period is about 2s. The time of 100 oscillations is measured by a stop watch of least count 0.1 s. The percentage error in g is
Here % error in l = and % error in T =
% error in g = % error in l + 2(% error in T)
= 0.2 %