When you are describing the rate that a race car goes around a track, should you use the term speed or velocity to describe the motion? Can the velocity of the car change without changing the average speed of the car?
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Main Entry: ve·loc·i·ty
Pronunciation: v&-'lä-s&-tE, -'läs-tE
Function: noun
Inflected Form(s): plural -ties
Etymology: Middle French velocité, from Latin velocitat-, velocitas, from veloc-, velox quick; probably akin to Latin vegEre to enliven —more at WAKE
Date: circa 1550
1 a : quickness of motion : SPEED <the velocity of sound> b : rapidity of movement <[my horse's]g strong suit is grace & personal comeliness, rather than velocity —Mark Twain> c : speed imparted to something <the power pitcher relies on velocity —Tony Scherman>
2 : the rate of change of position along a straight line with respect to time : the derivative of position with respect to time
3 a : rate of occurrence or action : RAPIDITY <the velocity of historical change —R. J. Lifton> <the narrative leaps from one frantic episode to another with impressive velocity —James Atlas> b : rate of turnover <the velocity of money>
Main Entry: [1]speed
Pronunciation: 'spEd
Function: noun
Etymology: Middle English spede, from Old English spEd; akin to Old High German spuot prosperity, speed, Old English spOwan to succeed, Latin spes hope, Lithuanian speti to be in time
Date: before 12th century
1 : archaic : prosperity in an undertaking : SUCCESS
2 a : the act or state of moving swiftly : SWIFTNESS b : rate of motion: as (1) : VELOCITY 1, 3a (2) : the magnitude of a velocity irrespective of direction c : IMPETUS
3 : swiftness or rate of performance or action
4 a : the sensitivity of a photographic film, plate, or paper expressed numerically b : the light-gathering power of a lens or optical system c : the time during which a camera shutter is open
5 : a transmission gear in automotive vehicles or bicycles — usually used in combination <a ten-speed bicycle>
6 : someone or something that appeals to one's taste
7 : METHAMPHETAMINE; also : a related stimulant drug and especially an amphetamine
synonym see HASTE
- speed·ster /'spEd-st&r/ noun
- at speed chiefly British : FAST, RAPIDLY
- up to speed : operating at full effectiveness or potential
Now you can make your own choice. Most people use the word "speed."
P.S. I forgot to mention another word my brothers (who race) use:
Main Entry: [1]rev
Pronunciation: 'rev
Function: noun
Etymology: short for revolution
Date: circa 1890
: a revolution of a motor
When describing the rate of a race car going around a track, the term "speed" is usually used rather than "velocity." Speed is a scalar quantity, which means it only takes into account the magnitude (amount) of the motion, whereas velocity is a vector quantity that includes both magnitude and direction.
The reason speed is commonly used when discussing race cars is because the direction of motion typically remains constant for a race car going around a track. Racetracks are typically circular or oval, so the direction is continuously changing, but on average, it is constant. Since the direction is not changing drastically throughout the race, it is more appropriate to describe the motion in terms of speed.
Regarding the second part of your question, yes, the velocity of the car can change without changing its average speed. This change in velocity can occur if the car changes its direction while maintaining roughly the same average speed. For example, if a car moves at a constant speed of 100 km/h around a circular track, its velocity is changing continuously because the direction is changing, even though the average speed remains the same. This is because velocity takes into account both speed and direction, while average speed only considers the overall displacement of the object over time.