When we use a tape timer to measure the acceleration due to gravity, the falling body experiences a periodic frictional force due to hitting of the timer, as well as a constant frictional force due to the contact of the paper tape with the timer through the tape attached to the body. The total effect approximates a constant effective frictional force of η_tot. The falling acceleration G is given by G = g -η_tot/m, which depends upon the mass m of the body. By fitting the experimental data for G versus m^-1, we obtain the acceleration due to gravity as g = 9.66±0.03 m/s² (with an error of 1.43 %) and the total effective friction as η_tot = 0.035  0.002 N.

Keywords: Acceleration due to gravity, Tape timer, Friction