5 Upwardly Launched Projectiles Conceptual Physics Text Correlation: Section 3.2
What determines whether the effects of air resistance are important or not? Answer: When the force of air resistance is small compared to the force that propels something, then motion is not appreciably different with or without air resistance. But when air resistance makes up a strong component in the net force on something, then it makes a difference. Question 1
Since in our everyday environment there is always air resistance on a projectile, why do we place so much importance on cases where air resistance is "negligible"? Answer: Because air resistance is a dominating influence on projectiles, particularly high-speed projectiles, it can obscure the physics of what is going on "beneath" the air drag. Galileo was one of the first to mentally strip away the air drag to see what was beneath. Question 2 • In this way he discovered the law of free fall and the law of inertia, both later embraced by Newton. Things can be complicated. We get a better grasp of them if we first understand the rules that apply when the complications are minimized. Being overwhelmed by the complications may prevent clear analysis.