Drag is a force that opposes motion through a fluid, acting between fluid layers, solid surfaces, or fluid-solid interfaces. This resistance force reduces the velocity of objects moving through fluids like air or water.
Types of Drag Creates Different Forces
Form and Skin Friction Generate Resistance
Form drag occurs due to an object’s size and shape, while skin friction drag results from fluid contact with surfaces. For example, a streamlined airplane wing experiences about 90% skin friction and 10% form drag, while a blunt cylinder faces 90% form drag and 10% skin friction.
Lift-Induced Drag Emerges from Flight
When aircraft generate lift, trailing vortices create additional drag. As the wing’s angle increases, both lift and induced drag increase until reaching the stalling angle. At this point, lift drops while pressure drag rises due to turbulent flow.
The Mathematics Behind Drag
The Drag Equation Quantifies Force
The drag force is calculated using: $$F_D = \frac{1}{2}\rho v^2C_DA$$
Where:
- $$\rho$$ is fluid density
- $$v$$ is object velocity
- $$A$$ is cross-sectional area
- $$C_D$$ is the drag coefficient
Power Requirements Scale Cubically
The power needed to overcome drag increases with the cube of velocity. A car at 50 mph might need 10 horsepower, but at 100 mph requires 80 horsepower to combat aerodynamic drag.
Terminal Velocity Limits Fall Speed
Objects falling through fluids reach a maximum speed called terminal velocity. For human-sized objects near Earth’s surface:
- Human body (~0.6m): ~70 m/s
- Cat (~0.2m): ~40 m/s
- Small bird (~0.05m): ~20 m/s
- Insect (~0.01m): ~9 m/s
Historical Development
Ludwig Prandtl’s boundary layer theory in the 1920s revolutionized our understanding of skin friction. Melvill Jones later demonstrated the critical importance of streamlining in aircraft design through his 1929 paper “The Streamline Airplane”.
Citations:
https://en.wikipedia.org/wiki/Drag
Merriam-Webster Online Dictionary
drag (noun)1.
something used to drag with , especially a device for under water to detect or obtain objects - dragging
2.
something that is , pulled, or drawn along or over a surface as - dragged
a) - harrow
b) a sledge for conveying heavy bodies
c) - conveyance
3.
a) the act or an instance of dragging or drawing as
(1) a drawing along or over a surface with effort or pressure
(2) motion effected with slowness or difficulty , also the condition of having or seeming to have such motion
(3) a draw on a pipe, cigarette, or cigar , also a draft of liquid
b) a movement, inclination, or retardation caused by or as if by dragging
c) slang influence securing special favor - pull
4.
a) something that retards motion, action, or advancement
b) (1) the retarding force acting on a body (as an airplane) moving through a fluid (as air) parallel and opposite to the direction of motion
(2) friction between engine parts , also retardation due to friction
c) - burden encumbrance the drag of population growth on living standards
d) one that is boring or gets in the way of enjoyment - thinks studying is a drag this sickly kid is going to be a social drag Edmund Morris
5.
a) an object drawn over the ground to leave a scented trail
b) a clog fastened to a trap to prevent the escape of a trapped animal
6.
- street road the main drag
7.
a) - costume outfit in Victorian drag
b) clothing typical of one sex worn by a person of the opposite sex - often used in the phrase in drag
8.
- drag race
transitive verb
1.
a) (1) to draw slowly or heavily - haul
(2) to cause (as oneself) to move with slowness or difficulty - dragged myself up the stairs
(3) to cause to trail along a surface - wandered off dragging the leash
b) (1) to bring by or as if by force or compulsion - had to drag her husband to the opera
(2) to extract by or as if by pulling
c) - protract drag a story out
2.
a) to pass a drag over - drag a field
b) to explore with a drag - drag a pond
c) to catch with a - dragnet
3.
to hit (a drag bunt) while moving toward first base
4.
intransitive verb
to move (items on a computer screen) especially by means of a mouse
1.
to hang or lag behind
2.
to fish or search with a drag
3.
to trail along on the ground
4.
a) to move slowly because of fatigue - was dragging after the long trip
b) to proceed or continue laboriously or tediously - the lawsuit dragged on for years
5.
- draw drag on a cigarette
6.
to make a plucking or pulling movement
7.
to participate in a drag race
of, being, involving, or intended for a person in drag - a drag ball
Merriam-Webster Online Thesaurus
drag (noun)1.
someone or something boring
SYNONYMS:
bore, drip, droner, dullsville, nudnik ( nudnick), snooze, snoozer, yawn, yawnerRELATED WORDS:
bummer, downer; bromide, pillNEAR ANTONYMS:
blast, gas [], kick, rush, upper2.
a passage cleared for public vehicular travel
SYNONYMS:
arterial, artery, avenue, boulevard, carriageway, drag, drive, expressway, freeway, high road, highway, pass, pike, road, roadway, route, row, street, thoroughfare, thruway, trace, turnpikeRELATED WORDS:
causeway; autobahn, autoroute, autostrada, dual carriageway [], interstate, motorway [], superhighway; beltway, bypass, parkway, ring road []; corniche, switchback; through street; high street [], Main Street; backstreet, branch, bystreet, byway, crossroad, secondary road, shunpike, side road, side street; alley, alleyway; circle, lane, laneway [], mews [], place; close [], cul-de-sac, dead end; corridor; track, trail3.
something that makes movement or progress difficult
SYNONYMS:
balk, bar, block, chain, clog, cramp, crimp, deterrent, drag, embarrassment, fetter, handicap, hindrance, holdback, hurdle, impediment, inhibition, interference, let, manacle, obstacle, obstruction, shackles, stop, stumbling block, trammelRELATED WORDS:
catch, hitch, rub, snag; barrier, blockade, blockage, brick wall, stone wall; arrest, bit, brake, check, constraint, curb, hobble, rein, restraint; embargo, stoppage; delay, holdup, stall; burden, cumber, load; danger, hazard, peril, reef; adversity, difficulty, disadvantage, drawback, hardshipNEAR ANTONYMS:
catalyst, goad, impetus, incentive, spur, stimulant, stimulus; advantage, break, edge; aid, assistance, benefit, boost, handmaiden ( handmaid), help4.
the portion of a serving of a beverage that is swallowed at one time
SYNONYMS:
belt, draft, drag, gulp, nip, quaff, shot, sip, slug, snort, sup, swallow, swig, swillRELATED WORDS:
dram, drop5.
a person who spoils the pleasure of others
SYNONYMS:
drag, grinch, party pooper, spoilsport, wet blanketRELATED WORDS:
fuddy-duddy, goody-goody, Goody Two-shoes, old maid, stick-in-the-mud; defeatist, Jeremiah, knocker, pessimist; complainer, crab, cynic, grouch, grump, sorehead, sourpuss, whiner; bore, downer, dripNEAR ANTONYMS:
cutup, jester, live wire; carouser, celebrant, celebrator, merrymaker, rejoicer, reveler ( reveller), roisterer; libertine, playboy, playgirl, rake6.
clothing chosen as appropriate for a specific situation
SYNONYMS:
costume, drag, dress, garb, getup, guise, togsRELATED WORDS:
apparel, attire, clothes, duds, habiliment(s), raiment; fashion, mode, style; array, caparison, vestments1.
to cause to follow by applying steady force on
SYNONYMS:
drag, draw, hale, haul, lug, tow, tugRELATED WORDS:
attract; heave, jerk, yank; carry, convey, ferry, move, transportNEAR ANTONYMS:
shove, thrust2.
to move or act slowly
SYNONYMS:
crawl, creep, dally, dawdle, diddle, dillydally, drag, lag, linger, loiter, lollygag ( lallygag), mope, poke, shilly-shally, tarryRELATED WORDS:
fiddle (around), fool around, mess around, monkey (around), play, potter (around), putter (around), trifle; hang (around out), idle, loaf, loll, lounge; amble, ease, inch, lumber, plod, saunter, shuffle, stagger, stroll; decelerate, slow (down up); filibuster, procrastinate, stall, temporizeNEAR ANTONYMS:
bowl, breeze, dart, hump, hurtle, hustle, scramble, stampede; gallop, jog, run, sprint, trot; accelerate, quicken, speed (up); catch up, fast-forward, outpace, outrun, outstrip, overtake3.
to move slowly
SYNONYMS:
creak (along), creep, drag, inch, limp, nose, ooze, plod, poke, slouch, snailRELATED WORDS:
lumber, shamble, shuffle, tramp, trudgeNEAR ANTONYMS:
float, glide, sail; hurry, tearto make longer
SYNONYMS:
drag (out), draw out, elongate, lengthen, outstretch, prolong, protract, stretchRELATED WORDS:
amplify, enlarge, expand, increase; attenuate, thinNEAR ANTONYMS:
decrease, diminish, lessen, reduce; thicken
Drag (Wiktionary)
English
Pronunciation
- enPR: drăg, IPA(key): /dɹæɡ/
- Rhymes: -æɡ
Etymology 1
From Middle English