2015-11-30T20:48:23Z

Jchintham3: Created page with "claimed by cshimkus3 ==Acceleration of Falling Objects== When you drop an object from a certain height off the ground, you can observe that the speed of the object does not r..."

claimed by cshimkus3
==Acceleration of Falling Objects==

When you drop an object from a certain height off the ground, you can observe that the speed of the object does not remain constant throughout that object's free fall. The object's speed changes as it falls and we know from the momentum principle that this is due to a net force acting on the object( Fnet = dp/dt ). If you drop an object from a tall enough starting height, you can also observe that the acceleration of the object is not constant either, so one can conclude that the net force on the object is not constant. An object falling towards the Earth's surface will not accelerate indefinitely, but will reach what is called ' ' terminal velocity ' '. Odds are you are familiar with the force of gravity, the force that holds you to Earth's surface and causes an object to accelerate initially downward. Gravity is defined as F=mg, where g is the acceleration constant of 9.8 m/s^2 (on Earth), and is a constant force. Another force, friction, is also acting on a falling object, however. This friction is due to the contact between molecules of the falling object and air molecules and is non-constant through the objects free-fall. In the following sections we will look into greater detail the effects of friction due to air.

===Falling Objects in a Vacuum===

As stated above, the force due to gravity on an object is constant. This can be proven by an object that is in free fall and is also in a vacuum. When an object is falling within a vacuum, it can be observed to have constant acceleration of 9.8 m/s^2 regardless of its mass or size. In the following video, a feather and a ball bearing are dropped inside a vacuum. See how both objects fall at the same rate. (Click on the picture)

[[File:Ballfeather.jpg |link=https://www.youtube.com/watch?v=_XJcZ-KoL9o ]]

===Friction Due to Air===
The friction due to air is a non-constant force on a falling object, and is related to multiple factors, such as cross-sectional area, the objects velocity, and the density of air. The force of air on a falling object is defined by the following equation in the opposite direction of the objects motion:

[[File:Airforce.gif]]

C is the numerical drag coeffecient which is dependent on the shape of the object.

So, when the force of air comes into play, we see the the feather and ball bearing will not fall at the same rate because they have different cross sectional areas. The following video shows a feather and ball bearing being dropped in both scenarios.

[[File:ballfeather2.jpg |link:https://www.youtube.com/watch?v=4z8g8OSOMzY ]]

As stated above, the force of air on a falling object is also dependent on the speed of a falling object. In that respect, we come to discuss terminal velocity. The force of air increases quadraticly with the speed of a falling object, so while the force of gravity remains constant, the force of air resistance will increase until the two forces perfectly cancel each other out and the net force is zero. At this point, the acceleration of an object is zero and the object has reached terminal velocity. You may ask "Why will the force of air not exceed the force of gravity?". This is because the force of air only continues to increase as the speed of the falling object increases and as the magnitude of the net force decreases, the speed of the object will approach being constant. Therefor, the magnitude of the force of air will also approach being constant. An object's terminal velocity can be defined by the following equation:

[[File:terminalvelocity.gif]]

==Where does that energy go?==

When we think of the energy of a falling object from the stance of a point-particle system, it will seem that some of the energy will disappear. When a falling object reaches terminal velocity, its kinetic energy remains constant while its potential energy due to gravity decreases. So, where does this energy go? We can now think of the falling object as an extended system and see that this energy get converted to internal energy as heat. The friction between the air and the falling object creates heat that takes the form of the ''lost'' energy. In a vacuum, this would not happen. The gravitational and kinetic energy of an object in a vacuum would vary inversely with one another.

===A Graphical Interpretation===

The following graphs will help you better understand the motion and energy relationships of a falling object.

A) 5 kg Ball Falling in Vacuum: Velocity vs Height

[[File:Velocity_ball_vacuum.png|thumb|center|1100x510px]]

B) 5 kg Ball Falling in Air

[[File:Velocity_ball_air.jpg|thumb|center|1100x510px]]

C) .5 kg Feather Falling in Vacuum

[[File:Velocity_ball_vacuum.png|thumb|center|1100x510px]]

D) .5 kg Feather Falling in Air

[[File:Velocity_feather_air.png|thumb|center|1100x510px]]

E) Energy of Ball Falling in Vacuum: Energy vs Time
(yellow=total, red=kinetic, blue=thermal, cyan=potential)

[[File:Energy_vacuum.png|thumb|center|1100x510px]]

F) Energy of Ball Falling in Air

[[File:Energy_air.png|thumb|center|1100x510px]]

===Examples===

'''Skydiver''': Think of a free-falling skydiver. When he/she is falling with their arms and legs stretched out like a star, they will accelerate until he or she reaches their terminal velocity. Now, what would happen if the free-faller pulled in his/her arms and legs and leans forward so that their body is more parallel with their free-fall? From our definition of terminal velocity defined above, we know that this speed is inversely dependent on the surface area of the falling object. So, we can infer that the skydiver would speed up, because when he/she bring their arms and legs in, they decrease their surface area perpendicular to the fall and therefor increase their terminal velocity.

[[File:Skydiver2.jpg|thumb|center|600x310px]]

'''Heat of Spacecraft''': Think of a spacecraft re-entering the Earth's atmosphere. How would the engineers designing that spacecraft need to determine the temperature that the space craft material needs to withstand. Well, these engineers could use the energy principle and the specific heat of the building material to do so. By calculating the terminal velocity, the initial potential and kinetic energy of the space craft when it enters the Earth's gravitational pull, and then graphing all the energy as at the space ship plummets to Earth's surface, these engineers can determine the heat this building material must be able to withstand.

[[File:Reentry2.jpg|thumb|center|600x310px]]

==Connectedness==
#How is this topic connected to something that you are interested in?
I have always been interested in skydiving and this topic is a vital concept for the spot. Just as in the example above, the way a skydiver positions their body determines how fast they will fall.
#How is it connected to your major?
#Is there an interesting industrial application?

==History==

Thermodynamics was brought up as a science in the 18th and 19th centuries. However, it was first brought up by Galilei, who introduced the concept of temperature and invented the first thermometer. G. Black first introduced the word 'thermodynamics'. Later, G. Wilke introduced another unit of measurement known as the calorie that measures heat. The idea of thermodynamics was brought up by Nicolas Leonard Sadi Carnot. He is often known as "the father of thermodynamics". It all began with the development of the steam engine during the Industrial Revolution. He devised an ideal cycle of operation. During his observations and experimentations, he had the incorrect notion that heat is conserved, however he was able to lay down theorems that led to the development of thermodynamics. In the 20th century, the science of thermodynamics became a conventional term and a basic division of physics. Thermodynamics dealt with the study of general properties of physical systems under equilibrium and the conditions necessary to obtain equilibrium.

== See also ==

Are there related topics or categories in this wiki resource for the curious reader to explore? How does this topic fit into that context?

===Further reading===

Books, Articles or other print media on this topic

===External links===

Internet resources on this topic

==References==

https://www.grc.nasa.gov/www/k-12/airplane/thermo0.html
http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/thereq.html
https://www.grc.nasa.gov/www/k-12/airplane/thermo2.html
http://www.phys.nthu.edu.tw/~thschang/notes/GP21.pdf
http://www.eoearth.org/view/article/153532/

[[Category:Which Category did you place this in?]]

Main Page

2015-11-30T20:48:13Z

Jchintham3: /* Interactions */

__NOTOC__
Welcome to the Georgia Tech Wiki for Intro Physics. This resources was created so that students can contribute and curate content to help those with limited or no access to a textbook. When reading this website, please correct any errors you may come across. If you read something that isn't clear, please consider revising it!

Looking to make a contribution?
#Pick a specific topic from intro physics
#Add that topic, as a link to a new page, under the appropriate category listed below by editing this page.
#Copy and paste the default [[Template]] into your new page and start editing.

Please remember that this is not a textbook and you are not limited to expressing your ideas with only text and equations. Whenever possible embed: pictures, videos, diagrams, simulations, computational models (e.g. Glowscript), and whatever content you think makes learning physics easier for other students.

== Source Material ==
All of the content added to this resource must be in the public domain or similar free resource. If you are unsure about a source, contact the original author for permission. That said, there is a surprisingly large amount of introductory physics content scattered across the web. Here is an incomplete list of intro physics resources (please update as needed).
* A physics resource written by experts for an expert audience [https://en.wikipedia.org/wiki/Portal:Physics Physics Portal]
* A wiki book on modern physics [https://en.wikibooks.org/wiki/Modern_Physics Modern Physics Wiki]
* The MIT open courseware for intro physics [http://ocw.mit.edu/resources/res-8-002-a-wikitextbook-for-introductory-mechanics-fall-2009/index.htm MITOCW Wiki]
* An online concept map of intro physics [http://hyperphysics.phy-astr.gsu.edu/hbase/hph.html HyperPhysics]
* Interactive physics simulations [https://phet.colorado.edu/en/simulations/category/physics PhET]
* OpenStax algebra based intro physics textbook [https://openstaxcollege.org/textbooks/college-physics College Physics]
* The Open Source Physics project is a collection of online physics resources [http://www.opensourcephysics.org/ OSP]
* A resource guide compiled by the [http://www.aapt.org/ AAPT] for educators [http://www.compadre.org/ ComPADRE]

== Organizing Categories ==
These are the broad, overarching categories, that we cover in two semester of introductory physics. You can add subcategories or make a new category as needed. A single topic should direct readers to a page in one of these catagories.

<div class="toccolours mw-collapsible mw-collapsed">
===Interactions===
<div class="mw-collapsible-content">
*[[Kinds of Matter]]
*[[Detecting Interactions]]
*[[Fundamental Interactions]]
*[[System & Surroundings]]
*[[Newton's First Law of Motion]]
*[[Newton's Second Law of Motion]]
*[[Newton's Third Law of Motion]]
*[[Gravitational Force]]
*[[Terminal Speed]]
*[[Simple Harmonic Motion]]
*[[Speed and Velocity]]
*[[Electric Polarization]]

</div>
</div>

<div class="toccolours mw-collapsible mw-collapsed">

===Theory===
<div class="mw-collapsible-content">
*[[Einstein's Theory of Special Relativity]]
*[[Quantum Theory]]
*[[Big Bang Theory]]

</div>
</div>

<div class="toccolours mw-collapsible mw-collapsed">

===Notable Scientists===
<div class="mw-collapsible-content">
*[[Albert Einstein]]
*[[Ernest Rutherford]]
*[[Joseph Henry]]
*[[Michael Faraday]]
*[[J.J. Thomson]]
*[[James Maxwell]]
*[[Robert Hooke]]
*[[Carl Friedrich Gauss]]
*[[Nikola Tesla]]
*[[Andre Marie Ampere]]
*[[Sir Isaac Newton]]
*[[J. Robert Oppenheimer]]
*[[Oliver Heaviside]]
*[[Rosalind Franklin]]
*[[Erwin Schrödinger]]
*[[Enrico Fermi]]
*[[Robert J. Van de Graaff]]
*[[Charles de Coulomb]]
*[[Hans Christian Ørsted]]
*[[Philo Farnsworth]]
*[[Niels Bohr]]
*[[Georg Ohm]]
*[[Galileo Galilei]]
*[[Gustav Kirchhoff]]
*[[Max Planck]]
*[[Heinrich Hertz]]
*[[Edwin Hall]]
*[[James Watt]]
*[[Count Alessandro Volta]]
*[[Josiah Willard Gibbs]]
*[[Richard Phillips Feynman]]
*[[Sir David Brewster]]
*[[Daniel Bernoulli]]
*[[William Thomson]]
</div>
</div>

<div class="toccolours mw-collapsible mw-collapsed">

===Properties of Matter===
<div class="mw-collapsible-content">
*[[Mass]]
*[[Velocity]]
*[[Relative Velocity]]
*[[Density]]
*[[Charge]]
*[[Spin]]
*[[SI Units]]
*[[Heat Capacity]]
*[[Specific Heat]]
*[[Wavelength]]
*[[Conductivity]]
</div>
</div>

<div class="toccolours mw-collapsible mw-collapsed">

===Contact Interactions===
<div class="mw-collapsible-content">
* [[Young's Modulus]]
* [[Friction]]
* [[Tension]]
* [[Hooke's Law]]
*[[Centripetal Force and Curving Motion]]
*[[Compression or Normal Force]]
* [[Length and Stiffness of an Interatomic Bond]]
</div>
</div>

<div class="toccolours mw-collapsible mw-collapsed">

===Momentum===
<div class="mw-collapsible-content">
* [[Vectors]]
* [[Kinematics]]
* [[Conservation of Momentum]]
* [[Predicting Change in multiple dimensions]]
* [[Momentum Principle]]
* [[Impulse Momentum]]
* [[Curving Motion]]
* [[Multi-particle Analysis of Momentum]]
* [[Iterative Prediction]]
* [[Newton's Laws and Linear Momentum]]
</div>
</div>

<div class="toccolours mw-collapsible mw-collapsed">

===Angular Momentum===
<div class="mw-collapsible-content">
* [[The Moments of Inertia]]
* [[Rotation]]
* [[Torque]]
*[[Systems with Zero Torque]]
*[[Systems with Nonzero Torque]]
* [[Right Hand Rule]]
* [[Angular Velocity]]
* [[Predicting a Change in Rotation]]
* [[Conservation of Angular Momentum]]
*[[Rotational Angular Momentum]]
*[[Total Angular Momentum]]

</div>
</div>

<div class="toccolours mw-collapsible mw-collapsed">

===Energy===
<div class="mw-collapsible-content">
*[[The Energy Principle]]
*[[Predicting Change]]
*[[Rest Mass Energy]]
*[[Kinetic Energy]]
*[[Potential Energy]]
*[[Work]]
*[[Thermal Energy]]
*[[Conservation of Energy]]
*[[Electric Potential]]
*[[Energy Transfer due to a Temperature Difference]]
*[[Gravitational Potential Energy]]
*[[Point Particle Systems]]
*[[Real Systems]]
*[[Spring Potential Energy]]
*[[Internal Energy]]
*[[Translational, Rotational and Vibrational Energy]]
*[[Franck-Hertz Experiment]]
*[[Power]]
*[[Energy Graphs]]
*[[Air Resistance]]
*[[Electronic Energy Levels]]
*[[Second Law of Thermodynamics and Entropy]]
*[[Specific Heat Capacity]]
*[[Quantized Energy Levels]]
</div>
</div>

<div class="toccolours mw-collapsible mw-collapsed">

===Collisions===
<div class="mw-collapsible-content">
*[[Collisions]]
*[[Maximally Inelastic Collision]]
*[[Elastic Collisions]]
*[[Inelastic Collisions]]
*[[Head-on Collision of Equal Masses]]
*[[Head-on Collision of Unequal Masses]]
*[[Rutherford Experiment and Atomic Collisions]]
</div>
</div>

<div class="toccolours mw-collapsible mw-collapsed">

===Fields===
<div class="mw-collapsible-content">
* [[Electric Field]] of a
** [[Point Charge]]
** [[Electric Dipole]]
** [[Capacitor]]
** [[Charged Rod]]
** [[Charged Ring]]
** [[Charged Disk]]
** [[Charged Spherical Shell]]
** [[Charged Cylinder]]
**[[A Solid Sphere Charged Throughout Its Volume]]
*[[Electric Potential]]
**[[Potential Difference in a Uniform Field]]
**[[Potential Difference of point charge in a non-Uniform Field]]
**[[Sign of Potential Difference]]
**[[Potential Difference in an Insulator]]
*[[Electric Force]]
*[[Polarization]]
*[[Charge Motion in Metals]]
*[[Magnetic Field]]
**[[Right-Hand Rule]]
**[[Direction of Magnetic Field]]
**[[Magnetic Field of a Long Straight Wire]]
**[[Magnetic Field of a Loop]]
**[[Bar Magnet]]
**[[Magnetic Force]]
**[[Hall Effect]]
**[[Lorentz Force]]
**[[Biot-Savart Law]]
**[[Biot-Savart Law for Currents]]
**[[Integration Techniques for Magnetic Field]]
**[[Sparks in Air]]
**[[Motional Emf]]
**[[Detecting a Magnetic Field]]
**[[Moving Point Charge]]
**[[Non-Coulomb Electric Field]]
**[[Motors and Generators]]
</div>
</div>

<div class="toccolours mw-collapsible mw-collapsed">

===Simple Circuits===
<div class="mw-collapsible-content">
*[[Components]]
*[[Steady State]]
*[[Non Steady State]]
*[[Node Rule]]
*[[Loop Rule]]
*[[Power in a circuit]]
*[[Ammeters,Voltmeters,Ohmmeters]]
*[[Current]]
*[[Ohm's Law]]
*[[Series Circuits]]
*[[RC]]
*[[Circular Loop of Wire]]
*[[RL Circuit]]
*[[LC Circuit]]
*[[Surface Charge Distributions]]
*[[Feedback]]
*[[Transformers]]
</div>

<div class="toccolours mw-collapsible mw-collapsed">

===Maxwell's Equations===
<div class="mw-collapsible-content">
*[[Gauss's Flux Theorem]]
**[[Electric Fields]]
**[[Magnetic Fields]]
*[[Ampere's Law]]
**[[Magnetic Field of Coaxial Cable Using Ampere's Law]]
*[[Faraday's Law]]
**[[Curly Electric Fields]]
**[[Inductance]]
**[[Lenz's Law]]
***[[Lenz Effect and the Jumping Ring]]
**[[Motional Emf using Faraday's Law]]
*[[Ampere-Maxwell Law]]
**[[Superconducters]]
</div>
</div>

<div class="toccolours mw-collapsible mw-collapsed">

===Radiation===
<div class="mw-collapsible-content">
*[[Producing a Radiative Electric Field]]
*[[Sinusoidal Electromagnetic Radiaton]]
*[[Lenses]]
*[[Energy and Momentum Analysis in Radiation]]
*[[Electromagnetic Propagation]]
*[[Snell's Law]]
*[[Light Propagation Through a Medium]]
</div>
</div>
<div class="toccolours mw-collapsible mw-collapsed">

===Sound===
<div class="mw-collapsible-content">
*[[Doppler Effect]]
*[[Nature, Behavior, and Properties of Sound]]
*[[Resonance]]
*[[Sound Barrier]]
</div>
</div>
*[[blahb]]
</div>
</div>

== Resources ==
* Commonly used wiki commands [https://en.wikipedia.org/wiki/Help:Cheatsheet Wiki Cheatsheet]
* A guide to representing equations in math mode [https://en.wikipedia.org/wiki/Help:Displaying_a_formula Wiki Math Mode]
* A page to keep track of all the physics [[Constants]]
* An overview of [[VPython]]

Main Page

Air Resistance

2015-11-30T02:42:51Z

Jchintham3: /* The Main Idea */