Which encounters the greater force of air resistance

Air resistance is the result of an object plowing through a layer of air and colliding with air molecules. The more air molecules which an object collides with, the greater the air resistance force. Subsequently, the amount of air resistance is dependent upon the speed of the falling object and the surface area of the falling object. Based on surface area alone, it is safe to assume that for the same speed the elephant would encounter more air resistance than the feather.

Answering these questions demands an understanding of Newton's first and second law and the concept of terminal velocity. According to Newton's laws, an object will accelerate if the forces acting upon it are unbalanced; and further, the amount of acceleration is directly proportional to the amount of net force unbalanced force acting upon it.

Falling objects initially accelerate gain speed because there is no force big enough to balance the downward force of gravity.

Yet as an object gains speed, it encounters an increasing amount of upward air resistance force. In fact, objects will continue to accelerate gain speed until the air resistance force increases to a large enough value to balance the downward force of gravity.

Since the elephant has more mass, it weighs more and experiences a greater downward force of gravity. The elephant will have to accelerate gain speed for a longer period of time before there is sufficient upward air resistance to balance the large downward force of gravity. Once the upward force of air resistance upon an object is large enough to balance the downward force of gravity, the object is said to have reached a terminal velocity.

The terminal velocity is the final velocity of the object; the object will continue to fall to the ground with this terminal velocity. In the case of the elephant and the feather, the elephant has a much greater terminal velocity than the feather.

As mentioned above, the elephant would have to accelerate for a longer period of time. The elephant requires a greater speed to accumulate sufficient upward air resistance force to balance the downward force of gravity.

If you wish to download it, please recommend it to your friends in any social system. Share buttons are a little bit lower. Thank you! Published by Wilfred Park Modified over 5 years ago. True or false:. Drawing free-body diagrams: Air resistance, free fall, terminal velocity and friction Most of the information is from:. Falling Objects and Gravity. Air Resistance When an object falls, gravity pulls it down.

Air resistance works opposite of gravity and opposes the motion. In most situations, at least two forces act on any object. The overall effect of these forces makes it act differently. What then? There is a problem. Air resistance is a force that depends on the velocity.

This means that the force and thus the acceleration is not constant. That's a big problem. We can still solve this with a numerical calculations. In short, I can use a computer to model just a tiny time interval for a falling object. During this short time interval, the forces are roughly constant. Here is an older post that gives an introduction to numerical calculations. Also, don't forget that my ebook Just Enough Physics has a whole chapter on numerical calculations.

Let's just get to the calculation. Here is a model of a ping pong ball falling from a height of 10 meters. Actually, this is a Glowscript program so you can run it yourself and even edit it. Try it! In this calculation, I have a ping pong ball and a ball without air resistance dropped from the same height.

In this plot, you can see that the ping pong ball hits after the no-air resistance ball with a time difference of 0. But this doesn't answer the question: how high is too high? Of course, there isn't just one answer to this question. The maximum height depends on how accurate you want your model.

Here is the real plot that you want. This shows the falling time difference between an object with air resistance and one without for different starting heights. Actually, since larger starting heights will have larger times, I have plotted the fractional difference in times. If you are just getting a rough estimate like falling off a building , it would probably be fine to ignore air resistance. If you were dropping a ping pong ball instead, I would assume no air resistance for heights around just 4 meters.

But it's not just about the falling time.