1. How fast would a textbook be falling after 10 seconds dropped from rest?
2. Now suppose you dropped a feather instead of a textbook. How fast would the feather be falling after 10 seconds, assuming there was no friction due to air?
The last worked example with the feather is a tricky one – we usually think of a feather floating slowly and gently to the ground, rather than speeding up as it falls. This is because the molecules in the air around us push on objects as they fall. Those air molecules push in all directions, and some actually push upward on the falling objects, counteracting the force of gravity. This upward force from the air is very noticeable in the case of a feather, partly due to its small mass and partly due to its shape. In the absence of air, a feather would accelerate as it falls in just the same way as a more massive object, such as a textbook. Scientists have tested this by observing the way objects fall in vacuum chambers.