In Galileo’s inclined-plane experiments, the acceleration of a ball rolling down a smooth ramp stayed approximately constant.
Galileo used inclined planes to slow falling motion enough for timing and measurement. He found that the distance traveled increased in proportion to the square of elapsed time, a relationship associated with uniformly accelerated motion.
The ramp was not meant to make the acceleration identical to free fall. Instead, it provided a practical way to study the same general behavior at a slower rate. Galileo’s work helped replace purely qualitative descriptions of motion with mathematical laws.
A common story says Galileo dropped objects from the Leaning Tower of Pisa, but the inclined-plane investigations provide the clearer experimental basis for his quantitative analysis of falling bodies.