Gravitational Acceleration
Galileo's hypothesis:
free fall is at constant acceleration `g`.
Where `g` is the acceleration due to gravity on the Earth. Its magnitude is approximately
` g = 9.80\ m//s^2` at surface of Earth
Experiment
A rock and a feather are dropped simultaneously
(a) in air (Air-filled tube),
(b) in a vacuum(Evacuated tube).
Galileo's specific contribution to our understanding of the motion of falling object can be summarized as following:
at a given location on the Earth and in the absence of air resistance, all objects fall with the same constant acceleration.