How are the troposphere, stratosphere, and thermosphere important for supporting life on Earth? Which layer of the atmosphere is likely the most important for life on Earth?

The troposphere contains 75% of the atmospheric mass as well as the oxygen and carbon dioxide plants and animals need to survive. The stratosphere's ozone layer absorbs ultraviolet radiation which is harmful to living organisms. The thermosphere absorbs solar radiation and helps to regulate the Earth's temperature. All layers of the atmosphere are important for supporting life on the Earth, but the troposphere is the most important as it provides organisms with the air they breathe.

air exerts forces on falling objects near earth’s surface.

explanation:

the term 'free falls' refer to object that are falling towards the earth, in a situation in which gravity is the only force acting on the object.

for an object in free fall, the acceleration is constant (g, the gravitational acceleration), and so the velocity of the object constantly increases.

for objects near earth's surface, there is always another force acting on the object: the resistance due to the air. this force is opposed to the direction of fall of the object, and it is proportional to the velocity of the object, so as the object falls down, this force increases up to a point when it balances the force of gravity, and the object continues its motion at constant velocity (called terminal velocity). since in this case gravity is not the only force acting on the object, we are not in a situation of free fall.