Help? ( if you do not know the answer please do not add your answer. I will mark brainliest if the answer is correct, If you guess and cause me to get this question wrong; i will report your answer. Please don't waste my time or anyone elses, Thanks. )

The famous scientist galileo galilei did several experiments with sloping planes, which he rolled metal balls down so that he could study motion. by changing the slope, he could study how the speed at which the ball rolled was affected. what was the dependent variable in galileo's experiment?