You have two identical tennis balls and fill one with water. You release both balls simultaneously from the top of a tall building. If air resistance is negligible, which ball will strike the ground first? Explain. What if air resistance is ?not? negligible?
Solution 28DQ If they were for example in a vacuum then as gravity acts proportionally then they would hit the ground at the same time.this means if air resistance is negligible both will hit the ground at the same time. However if both balls are same size and one filled with water they will both fall accelerating till they reach terminal velocity which is proportional to force and drag and is reached both are in balance. As the force higher with the water filled tennis ball so it hits ground first when air resistance is not negligible. For these objects,the gravitational force is huge in comparison to the air resistance force.essentially it doesn't do much change to the falling acceleration of these two objects.but it matters when air resistance concept occurs.for anything at low speed will have a negligible air resistance and high speed will have significant air resistance.some examples where you do not neglect air resistance are: 1.A falling piece of paper or feather. 2.A ping pong ball. 3.A falling human at high speeds. 4.A professionally thrown base ball (100 mph). 5.Tiny rocks or gravy. In many situations where a heavier object does indeed hit the ground before a lighter object(because of air resistance).