speed

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speed,

change in distance with respect to time. Speed is a scalar rather than a vectorvector,
quantity having both magnitude and direction; it may be represented by a directed line segment. Many physical quantities are vectors, e.g., force, velocity, and momentum.
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 quantity; i.e., the speed of a body tells one how fast the body is moving but not the direction of the motion. If during time t a body travels over a distance s, then the average speed of that body is equal to s/t. The speed and direction of a body's motion together determine the body's velocityvelocity,
change in displacement with respect to time. Displacement is the vector counterpart of distance, having both magnitude and direction. Velocity is therefore also a vector quantity. The magnitude of velocity is known as the speed of a body.
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.

Speed

The time rate of change of position of a body without regard to direction. It is the numerical magnitude only of a velocity and hence is a scalar quantity. Linear speed is commonly measured in such units as meters per second, miles per hour, or feet per second.

Average linear speed is the ratio of the length of the path traversed by a body to the elapsed time during which the body moved through that path. Instantaneous speed is the limiting value of the foregoing ratio as the elapsed time approaches zero. See Velocity

speed

[spēd]
(graphic arts)
The sensitivity of a photographic film, expressed according to one of several scales.
(mechanics)
The time rate of change of position of a body without regard to direction; in other words, the magnitude of the velocity vector.
(optics)
The light-gathering power of a lens, expressed as the reciprocal of the f number.
The time that a camera shutter is open.
(physics)
In general, the rapidity with which a process takes place.

Speed

an “illiterate loiterer”; slow-moving servant. [Br. Lit.: Two Gentlemen of Verona]

speed

1. Physics
a. a scalar measure of the rate of movement of a body expressed either as the distance travelled divided by the time taken (average speed) or the rate of change of position with respect to time at a particular point (instantaneous speed). It is measured in metres per second, miles per hour, etc.
b. (not in technical usage) another word for velocity
2. a rate of rotation, usually expressed in revolutions per unit time
3. a gear ratio in a motor vehicle, bicycle, etc.
4. Photog a numerical expression of the sensitivity to light of a particular type of film, paper, or plate
5. Photog a measure of the ability of a lens to pass light from an object to the image position, determined by the aperture and also the transmitting power of the lens. It increases as the f-number is decreased and vice versa
6. a slang word for amphetamine

SPEED

Early system on LGP-30. Listed in CACM 2(5):16 (May 1959).
References in periodicals archive ?
But Reneman said she's "pretty sure the effects are due to methylphenidate and not something else," since prior research had produced similar results.
But in adults, amphetamines, bupropion, and methylphenidate all beat placebo.
Based upon this information, the researchers urge clinicians to be cautious in prescribing methylphenidate, and to weigh up the benefits and risks more carefully.
Recently, professional councils, the Ministry of Health and the National Health Council have started a movement that claims for efforts towards the construction of guidelines that support public policies for the rationalization of the use of the methylphenidate and the confrontation of situations of abuse (9).
Has amphetamine's neurotoxicity (relative to methylphenidate) been experimentally demonstrated?
Students using methylphenidate can experience numerous side-effects, such as hallucinations, anxiety, dry mouth and visual disturbances.
Elevated DaT levels result from up-regulation in the presence of chronic methylphenidate therapy, which accounts for early reports that demonstrated increased striatal DaT density.
Other than the concern for pregnancy loss, which could be explained in part by other characteristics of the mothers who were taking methylphenidate early in pregnancy, the limited data to date have been generally reassuring, with no suggestion of an overall increased risk for major congenital malformations or a specific pattern of defects.
"We are also aware of the possibility that methylphenidate could be diverted and abused, and for this reason we recommend that its use should be monitored carefully.
Each extended-release tablet contains 18 mg or 27 mg of methylphenidate hydrochloride as the active ingredient and is designed to be effective for 12 hours.
There have been reports over the past few decades about uses for stimulants, such as methylphenidate, for which they are not traditionally indicated and for which these drugs are not registered.
Methylphenidate is a stimulant drug that binds and inhibits the dopamine transporter (Gatley, Pan, Chen, Chaturvedi, & Ding, 1996; Schweri et al., 1985) and produces dopamine overflow in the striatum (Butcher, Liptrot, & Arbuthnott, 1991; Gerasimov et al., 2000; Hurd & Ungerstedt, 1989; Kuczenski & Segal, 1997; Volkow et al., 2001).