According to the Physical Activity Guidelines for Americans, adults need muscle-strengthening activities on __ or more days a week that work all major muscle groups (legs, hips, back, abdomen, chest, shoulders, and arms).

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?