Drag - Revision history

Jmdonev: 1 revision imported

2021-10-15T19:13:41Z

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energy>Jmdonev at 23:42, 27 May 2021

2021-05-27T23:42:00Z

← Older revision		Revision as of 23:42, 27 May 2021
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	[[Category:Done ~~2018~~-05-18]]		[[Category:Done 2021-01-31]]
	[[File:Volkswagen_XL1.jpg\|400px\|thumb\|right\|Figure 1. Cars are shaped optimally in order to minimize the drag force that they experience. Pictured above is the Volkswagen XL1, the most fuel efficient production vehicle. The XL1 gets this tittle with help from its extremely low drag coefficient, 0.189, lowest of any production vehicle.<ref>Wikimedia. (August 2, 2016). ''Volkswagen XL1'' [Online], Available: https://commons.wikimedia.org/wiki/File:Volkswagen_XL1.jpg</ref>]]		[[File:Volkswagen_XL1.jpg\|400px\|thumb\|right\|Figure 1. Cars are shaped optimally in order to minimize the drag force that they experience. Pictured above is the Volkswagen XL1, the most fuel efficient production vehicle. The XL1 gets this tittle with help from its extremely low drag coefficient, 0.189, lowest of any production vehicle.<ref>Wikimedia. (August 2, 2016). ''Volkswagen XL1'' [Online], Available: https://commons.wikimedia.org/wiki/File:Volkswagen_XL1.jpg</ref>]]
	<onlyinclude>'''Drag''' is a [[force]] that opposes or resists motion, caused by collisions of moving objects with [[molecule]]s in a [[fluid]] like [[air]] or [[water]]. It is similar to surface [[friction]] since both oppose motion, but drag occurs specifically in moving fluids.</onlyinclude> Drag increases if an object increases its [[speed]], has a large cross-sectional area, or if the fluid it is moving through is more [[density\|dense]].<ref name=Knight>R. D. Knight, "Drag" in ''Physics for Scientists and Engineers: A Strategic Approach,'' 3ed ed. San Francisco, U.S.A.: Pearson Addison-Wesley, 2008, ch.6, sec.5, pp. 152-154</ref>		<onlyinclude>'''Drag''' is a [[force]] that opposes or resists motion, caused by collisions of moving objects with [[molecule]]s in a [[fluid]] like [[air]] or [[water]]. It is similar to surface [[friction]] since both oppose motion, but drag occurs specifically in moving fluids.</onlyinclude> Drag increases if an object increases its [[speed]], has a large cross-sectional area, or if the fluid it is moving through is more [[density\|dense]].<ref name=Knight>R. D. Knight, "Drag" in ''Physics for Scientists and Engineers: A Strategic Approach,'' 3ed ed. San Francisco, U.S.A.: Pearson Addison-Wesley, 2008, ch.6, sec.5, pp. 152-154</ref>
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	where		where

			*<math>F_{drag}</math> is the drag force in the direction opposite to that of the velocity
			*<math>C</math> is the drag coefficient
	*<math>\rho</math> is the density of the fluid (air is 1.2 [[kilogram\|kg]]/[[meter\|m]]<sup>3</sup> at [[STP]] conditions)		*<math>\rho</math> is the density of the fluid (air is 1.2 [[kilogram\|kg]]/[[meter\|m]]<sup>3</sup> at [[STP]] conditions)
	*<math>A</math> is the cross-sectional area (see Figure 2)		*<math>A</math> is the cross-sectional area (see Figure 2)
	*<math>v</math> is the [[velocity]] of the object		*<math>v</math> is the [[velocity]] of the object
	*<math>C</math> is the drag coefficient
	*<math>F_{drag}</math> is the drag force in the direction opposite to that of the velocity

	This equation is an approximation and only works for ordinary objects (with a size between a few millimeters and a few meters) and ordinary speeds (no more than a several meters per second), so it fails to describe the motion of very small objects like dust, or very fast objects like bullets.<ref name=Knight/>		This equation is an approximation and only works for ordinary objects (with a size between a few millimeters and a few meters) and ordinary speeds (no more than a several meters per second), so it fails to describe the motion of very small objects like dust, or very fast objects like bullets.<ref name=Knight/>

Jmdonev: 1 revision imported

2018-05-18T22:53:06Z

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Jmdonev at 18:54, 11 May 2018

2018-05-11T18:54:22Z

← Older revision		Revision as of 18:54, 11 May 2018
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	[[Category:Done ~~2016~~-04-30]]		[[Category:Done 2018-05-18]]
	[[File:Volkswagen_XL1.jpg\|400px\|thumb\|right\|Figure 1. Cars are shaped optimally in order to minimize the drag force that they experience. Pictured above is the Volkswagen XL1, the most fuel efficient production vehicle. The XL1 gets this tittle with help from its extremely low drag coefficient, 0.189, lowest of any production vehicle.<ref>Wikimedia. (August 2, 2016). ''Volkswagen XL1'' [Online], Available: https://commons.wikimedia.org/wiki/File:Volkswagen_XL1.jpg</ref>]]		[[File:Volkswagen_XL1.jpg\|400px\|thumb\|right\|Figure 1. Cars are shaped optimally in order to minimize the drag force that they experience. Pictured above is the Volkswagen XL1, the most fuel efficient production vehicle. The XL1 gets this tittle with help from its extremely low drag coefficient, 0.189, lowest of any production vehicle.<ref>Wikimedia. (August 2, 2016). ''Volkswagen XL1'' [Online], Available: https://commons.wikimedia.org/wiki/File:Volkswagen_XL1.jpg</ref>]]
	<onlyinclude>'''Drag''' is a [[force]] that opposes or resists motion, caused by collisions of moving objects with [[molecule]]s in a [[fluid]] like [[air]] or [[water]]. It is ~~much like~~ surface [[friction]] ~~in that it opposes moving objects~~, ~~except that it~~ occurs in a moving ~~fluid~~.</onlyinclude> Drag increases if an object increases its [[speed]], has a large cross-sectional area, or if the fluid it is moving through is more [[density\|dense]].<ref name=Knight>R. D. Knight, "Drag" in ''Physics for Scientists and Engineers: A Strategic Approach,'' ~~3nd~~ ed. San Francisco, U.S.A.: Pearson Addison-Wesley, 2008, ch.6, sec.5, pp. 152-154</ref>		<onlyinclude>'''Drag''' is a [[force]] that opposes or resists motion, caused by collisions of moving objects with [[molecule]]s in a [[fluid]] like [[air]] or [[water]]. It is similar to surface [[friction]] since both oppose motion, but drag occurs specifically in moving fluids.</onlyinclude> Drag increases if an object increases its [[speed]], has a large cross-sectional area, or if the fluid it is moving through is more [[density\|dense]].<ref name=Knight>R. D. Knight, "Drag" in ''Physics for Scientists and Engineers: A Strategic Approach,'' 3ed ed. San Francisco, U.S.A.: Pearson Addison-Wesley, 2008, ch.6, sec.5, pp. 152-154</ref>

	Drag makes objects fall at different constant speeds, and causes energy loss in [[transportation]]. [[Gravity]], with no drag, makes all objects fall the same way: with an [[acceleration]] of [[Acceleration due to gravity\|9.8 m/s<sup>2</sup>]] towards the Earth. Therefore all objects should fall at the same pace, regardless of [[mass]], but clearly a feather falls differently than a brick. The drag acting on the object slows the falling objects.		Drag makes objects fall at different constant speeds, and causes energy loss in [[transportation]]. [[Gravity]], with no drag, makes all objects fall the same way: with an [[acceleration]] of [[Acceleration due to gravity\|9.8 m/s<sup>2</sup>]] towards the Earth. Therefore all objects should fall at the same pace, regardless of [[mass]], but clearly a feather falls differently than a brick. The drag acting on the object slows the falling objects.

	~~This article focuses on drag on cars; this takes into account a vehicle's aerodynamic characteristics. In addition to personal experience~~, wind tunnels making drag easy to ~~visualize~~.		Experimentally, wind tunnels like those in Figure 2 making drag easy to measure.

	==Equating==		==Equating==
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	The equation for the drag force depends on the three factors stated above, and can be written as:<ref name=Knight/><ref>Hyperphysics, ''Air Friction'' [Online], Available: http://hyperphysics.phy-astr.gsu.edu/hbase/airfri.html</ref>		The equation for the drag force depends on the three factors stated above, and can be written as:<ref name=Knight/><ref>Hyperphysics, ''Air Friction'' [Online], Available: http://hyperphysics.phy-astr.gsu.edu/hbase/airfri.html</ref>

	<center><m>F_{drag}=-\frac{1}{2}C\rho A v^2</m></center>		<center><math>F_{drag}=-\frac{1}{2}C\rho A v^2</math></center>

	where		where

	*<m>\rho</m> is the density of the fluid (air is 1.2 [[kilogram\|kg]]/[[meter\|m]]<sup>3</sup> at [[STP]] conditions)		*<math>\rho</math> is the density of the fluid (air is 1.2 [[kilogram\|kg]]/[[meter\|m]]<sup>3</sup> at [[STP]] conditions)
	*<m>A</m> is the cross-sectional area (see Figure 2)		*<math>A</math> is the cross-sectional area (see Figure 2)
	*<m>v</m> is the [[velocity]] of the object		*<math>v</math> is the [[velocity]] of the object
	*<m>C</m> is the drag coefficient		*<math>C</math> is the drag coefficient
	*<m>F_{drag}</m> is the drag force in the direction opposite to that of the velocity		*<math>F_{drag}</math> is the drag force in the direction opposite to that of the velocity

	This equation is an approximation and only works for ordinary objects (with a size between a few millimeters and a few meters) and ordinary speeds (no more than a several meters per second), so it fails to describe the motion of very small objects like dust, or very fast objects like bullets.<ref name=Knight/> ~~Moving quickly, means that the equations get more complicated.~~		This equation is an approximation and only works for ordinary objects (with a size between a few millimeters and a few meters) and ordinary speeds (no more than a several meters per second), so it fails to describe the motion of very small objects like dust, or very fast objects like bullets.<ref name=Knight/>

	The flow of air through a [[wind turbine]] causes the turbine to spin, because of the collision of the particles and the turbine. It might seem strange that a stationary object can be affected by air drag, but air drag occurs when there is a relative motion between the air and the object, so it can be viewed as if the turbine is moving through the stationary [[wind]]. The wind slows down upon contact with the turbine and these collisions combined with the shape of the turbine blades allows it to spin, providing [[wind power]].		The flow of air through a [[wind turbine]] causes the turbine to spin, because of the collision of the particles and the turbine. It might seem strange that a stationary object can be affected by air drag, but air drag occurs when there is a relative motion between the air and the object, so it can be viewed as if the turbine is moving through the stationary [[wind]]. The wind slows down upon contact with the turbine and these collisions combined with the shape of the turbine blades allows it to spin, providing [[wind power]].
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	===Drag coefficient (C)===		===Drag coefficient (C)===
	The drag coefficient in the equation for drag is quite complex, and depends on various factors such as those listed above, and also includes air viscosity and how ~~much it can be compressed~~.<ref>NASA, ''The Drag Coefficient'' [Online], Available: https://www.grc.nasa.gov/WWW/k-12/airplane/dragco.html</ref> It is usually determined experimentally, by taking measurements of an object in a wind chamber. ~~It can also be predicted by taking all of the factors into account, and NASA goes through~~ how ~~this~~ is ~~done~~ [https://www.grc.nasa.gov/WWW/k-12/airplane/dragco.html ~~here~~]. ~~Below is a picture of~~ various shapes and ~~their drag coefficients~~.		The drag coefficient in the equation for drag is quite complex, and depends on various factors such as those listed above, and also includes air viscosity and how compressible a fluid is.<ref>NASA, ''The Drag Coefficient'' [Online], Available: https://www.grc.nasa.gov/WWW/k-12/airplane/dragco.html</ref> It is usually determined experimentally, by taking measurements of an object in a wind chamber. For more details on how air drag is calculated please see [https://www.grc.nasa.gov/WWW/k-12/airplane/dragco.html NASA's site]. Figure 3 below shows the drag coefficient <math>C</math> for various shapes. Note that <math>C</math> has no units, and to calculate force one must multiply by the area in the figure as well.

	[[File:Drag.png\|thumb\|center\|770px\|Figure 3. Different objects have different drag coefficients~~, which~~ depends on their cross-sectional area and many other factors. The same object can have a different drag force as seen here.<ref>''Made internally by a member of the Energy Education team'', adapted from Physics for Scientists and Engineers by R. Knight.</ref>]]		[[File:Drag.png\|thumb\|center\|770px\|Figure 3. Different objects have different drag coefficients <math>C</math>. These coefficients depends on the shape of their cross-sectional area and many other factors. The same object can have a different drag force as seen here.<ref>''Made internally by a member of the Energy Education team'', adapted from Physics for Scientists and Engineers by R. Knight.</ref>]]

	==References==		==References==
	{{reflist}}[[Category:Uploaded]]		{{reflist}}[[Category:Uploaded]]

Jmdonev: 1 revision imported: From the summer

2016-09-17T22:29:41Z

1 revision imported: From the summer

← Older revision	Revision as of 22:29, 17 September 2016
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Jmdonev at 01:37, 4 August 2016

2016-08-04T01:37:39Z

← Older revision		Revision as of 01:37, 4 August 2016
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	[[Category:Done ~~2015~~-08-21]]		[[Category:Done 2016-04-30]]
	[[File:~~sprtscar~~.jpg\|~~300px~~\|thumb\|Figure 1. ~~Sports cars~~ are shaped optimally in order to minimize the drag force that they experience.<ref>~~lipetkd on Pixabay~~ [Online], Available: ~~http~~://~~pixabay~~.~~com~~/~~p-49278~~/~~?no_redirect~~</ref>]]		[[File:Volkswagen_XL1.jpg\|400px\|thumb\|right\|Figure 1. Cars are shaped optimally in order to minimize the drag force that they experience. Pictured above is the Volkswagen XL1, the most fuel efficient production vehicle. The XL1 gets this tittle with help from its extremely low drag coefficient, 0.189, lowest of any production vehicle.<ref>Wikimedia. (August 2, 2016). ''Volkswagen XL1'' [Online], Available: https://commons.wikimedia.org/wiki/File:Volkswagen_XL1.jpg</ref>]]
			<onlyinclude>'''Drag''' is a [[force]] that opposes or resists motion, caused by collisions of moving objects with [[molecule]]s in a [[fluid]] like [[air]] or [[water]]. It is much like surface [[friction]] in that it opposes moving objects, except that it occurs in a moving fluid.</onlyinclude> Drag increases if an object increases its [[speed]], has a large cross-sectional area, or if the fluid it is moving through is more [[density\|dense]].<ref name=Knight>R. D. Knight, "Drag" in ''Physics for Scientists and Engineers: A Strategic Approach,'' 3nd ed. San Francisco, U.S.A.: Pearson Addison-Wesley, 2008, ch.6, sec.5, pp. 152-154</ref>

	~~<onlyinclude>'''~~Drag~~''' is a~~ [[~~force~~]] ~~that opposes or resists motion, caused by collisions of moving objects with~~ [[~~molecule~~]]~~s in a~~ [[~~fluid~~]] ~~like air or~~ [[~~water~~]]. ~~It is much like surface~~ [[~~friction~~]] ~~in that it opposes moving objects~~, ~~except that it occurs in~~ a ~~moving fluid~~.~~</onlyinclude> Drag increases if an~~ object ~~increases its [[speed]], has~~ a ~~large cross-sectional area~~, ~~or if the fluid it is moving through is more~~ [[~~density~~\|~~dense]]~~.<ref ~~name=Knight~~>R. D. ~~Knight, "Drag" in~~ ''~~Physics for Scientists and Engineers: A Strategic Approach,~~'' ~~3nd ed. San Francisco~~, ~~U.S.A.~~: ~~Pearson Addison-Wesley, 2008, ch~~.~~6, sec.5, pp. 152~~-~~154~~</ref>		Drag makes objects fall at different constant speeds, and causes energy loss in [[transportation]]. [[Gravity]], with no drag, makes all objects fall the same way: with an [[acceleration]] of [[Acceleration due to gravity\|9.8 m/s<sup>2</sup>]] towards the Earth. Therefore all objects should fall at the same pace, regardless of [[mass]], but clearly a feather falls differently than a brick. The drag acting on the object slows the falling objects.

			This article focuses on drag on cars; this takes into account a vehicle's aerodynamic characteristics. In addition to personal experience, wind tunnels making drag easy to visualize.

			==Equating==
			[[File:xl1.jpg\|400px\|thumb\|right\|Figure 2. The Volkswagen XL1 in a wind tunnel where its streamlines can be seen clearly.<ref>ecomento. (August 2, 2016). ''Volkswagen XL1'' [Online], Available: http://ecomento.com/models/volkswagen-xl1/</ref>]]

	The equation for the drag force depends on the three factors stated above, and can be written as:<ref name=Knight/><ref>Hyperphysics, ''Air Friction'' [Online], Available: http://hyperphysics.phy-astr.gsu.edu/hbase/airfri.html</ref>		The equation for the drag force depends on the three factors stated above, and can be written as:<ref name=Knight/><ref>Hyperphysics, ''Air Friction'' [Online], Available: http://hyperphysics.phy-astr.gsu.edu/hbase/airfri.html</ref>
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	*<m>F_{drag}</m> is the drag force in the direction opposite to that of the velocity		*<m>F_{drag}</m> is the drag force in the direction opposite to that of the velocity

	This equation only works for ordinary objects (with a size between a few millimeters and a few meters) and ordinary speeds (no more than a ~~few hundred~~ meters per second), so it fails to describe the motion of very small objects like dust, or very fast objects like bullets.<ref name=Knight/>		This equation is an approximation and only works for ordinary objects (with a size between a few millimeters and a few meters) and ordinary speeds (no more than a several meters per second), so it fails to describe the motion of very small objects like dust, or very fast objects like bullets.<ref name=Knight/> Moving quickly, means that the equations get more complicated.

	The flow of air through a [[wind turbine]] causes the turbine to spin, because of the collision of the particles and the turbine. It might seem strange that a stationary object can be affected by air drag, but air drag occurs when there is a relative motion between the air and the object, so it can be viewed as if the turbine is moving through the stationary [[wind]]. The wind slows down upon contact with the turbine and these collisions combined with the shape of the turbine blades allows it to spin, providing [[wind power]].		The flow of air through a [[wind turbine]] causes the turbine to spin, because of the collision of the particles and the turbine. It might seem strange that a stationary object can be affected by air drag, but air drag occurs when there is a relative motion between the air and the object, so it can be viewed as if the turbine is moving through the stationary [[wind]]. The wind slows down upon contact with the turbine and these collisions combined with the shape of the turbine blades allows it to spin, providing [[wind power]].
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	The drag coefficient in the equation for drag is quite complex, and depends on various factors such as those listed above, and also includes air viscosity and how much it can be compressed.<ref>NASA, ''The Drag Coefficient'' [Online], Available: https://www.grc.nasa.gov/WWW/k-12/airplane/dragco.html</ref> It is usually determined experimentally, by taking measurements of an object in a wind chamber. It can also be predicted by taking all of the factors into account, and NASA goes through how this is done [https://www.grc.nasa.gov/WWW/k-12/airplane/dragco.html here]. Below is a picture of various shapes and their drag coefficients.		The drag coefficient in the equation for drag is quite complex, and depends on various factors such as those listed above, and also includes air viscosity and how much it can be compressed.<ref>NASA, ''The Drag Coefficient'' [Online], Available: https://www.grc.nasa.gov/WWW/k-12/airplane/dragco.html</ref> It is usually determined experimentally, by taking measurements of an object in a wind chamber. It can also be predicted by taking all of the factors into account, and NASA goes through how this is done [https://www.grc.nasa.gov/WWW/k-12/airplane/dragco.html here]. Below is a picture of various shapes and their drag coefficients.

	[[File:Drag.png\|thumb\|center\|770px\|Figure 2. Different objects have different drag coefficients, which depends on their cross-sectional area and many other factors. The same object can have a different drag force as seen here.<ref>''Made internally by a member of the Energy Education team'', adapted from Physics for Scientists and Engineers by R. Knight.</ref>]]		[[File:Drag.png\|thumb\|center\|770px\|Figure 3. Different objects have different drag coefficients, which depends on their cross-sectional area and many other factors. The same object can have a different drag force as seen here.<ref>''Made internally by a member of the Energy Education team'', adapted from Physics for Scientists and Engineers by R. Knight.</ref>]]

	==References==		==References==
	{{reflist}}[[Category:Uploaded]]		{{reflist}}[[Category:Uploaded]]

J.williams: 1 revision imported

2015-08-26T21:31:51Z

1 revision imported

← Older revision	Revision as of 21:31, 26 August 2015
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J.williams at 18:50, 24 August 2015

2015-08-24T18:50:38Z

New page

[[Category:Done 2015-08-21]]
[[File:sprtscar.jpg|300px|thumb|Figure 1. Sports cars are shaped optimally in order to minimize the drag force that they experience.<ref>lipetkd on Pixabay [Online], Available: http://pixabay.com/p-49278/?no_redirect</ref>]]

<onlyinclude>'''Drag''' is a [[force]] that opposes or resists motion, caused by collisions of moving objects with [[molecule]]s in a [[fluid]] like air or [[water]]. It is much like surface [[friction]] in that it opposes moving objects, except that it occurs in a moving fluid.</onlyinclude> Drag increases if an object increases its [[speed]], has a large cross-sectional area, or if the fluid it is moving through is more [[density|dense]].<ref name=Knight>R. D. Knight, "Drag" in ''Physics for Scientists and Engineers: A Strategic Approach,'' 3nd ed. San Francisco, U.S.A.: Pearson Addison-Wesley, 2008, ch.6, sec.5, pp. 152-154</ref>

The equation for the drag force depends on the three factors stated above, and can be written as:<ref name=Knight/><ref>Hyperphysics, ''Air Friction'' [Online], Available: http://hyperphysics.phy-astr.gsu.edu/hbase/airfri.html</ref>

<center><m>F_{drag}=-\frac{1}{2}C\rho A v^2</m></center>

where

*<m>\rho</m> is the density of the fluid (air is 1.2 [[kilogram|kg]]/[[meter|m]]<sup>3</sup> at [[STP]] conditions)
*<m>A</m> is the cross-sectional area (see Figure 2)
*<m>v</m> is the [[velocity]] of the object
*<m>C</m> is the drag coefficient
*<m>F_{drag}</m> is the drag force in the direction opposite to that of the velocity

This equation only works for ordinary objects (with a size between a few millimeters and a few meters) and ordinary speeds (no more than a few hundred meters per second), so it fails to describe the motion of very small objects like dust, or very fast objects like bullets.<ref name=Knight/>

The flow of air through a [[wind turbine]] causes the turbine to spin, because of the collision of the particles and the turbine. It might seem strange that a stationary object can be affected by air drag, but air drag occurs when there is a relative motion between the air and the object, so it can be viewed as if the turbine is moving through the stationary [[wind]]. The wind slows down upon contact with the turbine and these collisions combined with the shape of the turbine blades allows it to spin, providing [[wind power]].

Visit [https://www.grc.nasa.gov/www/k-12/airplane/drag1.html NASA] to read about aircraft drag.

===Drag coefficient (C)===
The drag coefficient in the equation for drag is quite complex, and depends on various factors such as those listed above, and also includes air viscosity and how much it can be compressed.<ref>NASA, ''The Drag Coefficient'' [Online], Available: https://www.grc.nasa.gov/WWW/k-12/airplane/dragco.html</ref> It is usually determined experimentally, by taking measurements of an object in a wind chamber. It can also be predicted by taking all of the factors into account, and NASA goes through how this is done [https://www.grc.nasa.gov/WWW/k-12/airplane/dragco.html here]. Below is a picture of various shapes and their drag coefficients.

[[File:Drag.png|thumb|center|770px|Figure 2. Different objects have different drag coefficients, which depends on their cross-sectional area and many other factors. The same object can have a different drag force as seen here.<ref>''Made internally by a member of the Energy Education team'', adapted from Physics for Scientists and Engineers by R. Knight.</ref>]]

==References==
{{reflist}}[[Category:Uploaded]]