If an object with mass is dropped from rest, one model for its speed after seconds, taking air resistance into account, is where is the acceleration due to gravity and is a positive constant. (In Chapter 9 we will be able to deduce this equation from the assumption that the air resistance is proportional to the speed of the object; is the proportionality constant.) Calculate . What is the meaning of this limit? For fixed , use l’Hospital’s Rule to calculate . What can you conclude about the velocity of a falling object in a vacuum?