# Air resistance vs. free fall

• itsme1
In summary, when throwing a ball upward with speed x, we can say that in the absence of air resistance, the ball will return at the same speed due to conservation of energy. However, in the presence of air resistance, the ball will come down at a slower speed with less kinetic energy due to friction with the air. The amount of energy lost is difficult to calculate and depends on various factors. This may be a homework question.

#### itsme1

if we throw upward a ball with speed x. What can we say about it when the ball returns in the presence of air resistance? What about in the absence?

itsme1 said:
if we throw upward a ball with speed x. What can we say about it when the ball returns in the presence of air resistance? What about in the absence?

In the absence of air resistance, it's easy - the ball comes back down at the same speed that it went up with. This follows from conservation of energy; the ball started with a certain amount of kinetic energy, traded the kinetic energy for potential energy as it climbed, and then reversed the trade and regained the kinetic energy on the way down.

In the presence of air resistance, the ball will come down at a slower speed and with less kinetic energy than it started with. The missing energy will have gone into friction with the air heating the ball and the air around it; the exact amount of energy lost will depend on many variables (the texture of the surface of the ball, the temperature and humidity, ...) and is generally hard to calculate.

That sounds like homework

## 1. What is air resistance and how does it affect free fall?

Air resistance is the force exerted by the air on a moving object. In free fall, the object is falling without any external forces acting on it besides gravity. Air resistance slows down the object's acceleration due to gravity, causing it to fall at a slower rate.

## 2. How does the shape and size of an object affect air resistance during free fall?

The shape and size of an object can greatly impact the amount of air resistance it experiences during free fall. Objects with a larger surface area, such as a feather, will experience more air resistance than objects with a smaller surface area, such as a rock. Additionally, objects with a streamlined shape, like a pencil, will experience less air resistance than objects with an irregular shape, like a crumpled piece of paper.

## 3. What factors can affect the amount of air resistance an object experiences during free fall?

The amount of air resistance an object experiences during free fall can be affected by several factors, including the object's shape and size, the density of the air, and the speed at which the object is falling. Other factors such as temperature, humidity, and air pressure can also play a role in the amount of air resistance experienced.

## 4. How does air resistance impact the speed of an object during free fall?

Air resistance acts in the opposite direction of the object's motion, so it can slow down the object's speed during free fall. As an object falls, it accelerates due to gravity, but as air resistance increases, the object's acceleration decreases. At a certain point, the force of gravity and the force of air resistance will balance out, causing the object to reach a terminal velocity, or a constant speed at which the forces are equal.

## 5. Can air resistance ever be completely eliminated during free fall?

No, air resistance cannot be completely eliminated during free fall. The only way to remove air resistance is to eliminate the medium of air, which is not possible on Earth. However, the effects of air resistance can be minimized by reducing the surface area and streamlining the shape of the falling object.