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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.
..... Click the link for more information. 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.
..... Click the link for more information. .
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
bandwidth(1) Computer people may use the term for capability and time. For example, "not enough bandwidth to get the job done" means not enough staff or time to do it. Its true meaning follows.
(2) The transmission capacity of an electronic pathway such as a communications line, computer bus or computer channel. Digital bandwidth is the number of pulses per second measured in bits per second (bps). For example, Ethernet transmits at different speeds, including 10 Mbps, 100 Mbps and 1000 Mbps (see Mbps and baseband).
When transmitting alternating frequencies, as with all wired analog, many wired digital and most wireless communications, the bandwidth is the difference between the highest and lowest frequencies, measured in cycles per second, or Hertz (Hz). For example, 802.11n Wi-Fi transmits in 20 MHz and 40 MHz channels within the 2.4 GHz and 5 GHz bands. The 20 and 40 MHz channel frequencies are the bandwidths, and each channel is divided into subchannels.
From Hertz to Bits - A Complicated Process
When using alternating frequencies for digital transmission, the frequencies are modified (modulated) by the digital input. Using the 802.11n Wi-Fi example, the resulting bit rate can range from 6.5 Mbps to 600 Mbps. This extremely wide range is determined by the signal strength and interference in the environment at any given moment. Any one of more than 30 combinations of channel bandwidth (20, 40 MHz), modulation scheme, error correction rate, channel spacing and number of antennas may be selected, on a packet-by-packet basis. See modulation, video bandwidth, space/time and bandwidth junkie.
|Bandwidth in Hertz to Bandwidth in Bits|
|This quadrature PSK (QPSK) example is one of the simplest modulation schemes. Each set of two input bits modifies the carrier into four phase angles. The amplitude remains constant, unlike QAM modulation, in which the amplitude is varied (see QAM).|
data rate(1) The speed at which data is transferred within the computer or between a peripheral device and the computer, measured in bytes per second. See transfer rate and space/time.
(2) The speed at which audio and video files are encoded (compressed), measured in bits per second (see bit rate).
(3) The transmission speed of a network. For example, 100Base-T Ethernet is rated at 100 Mbps (megabits per second). Also called "bit rate." See space/time.
space/timeThe following units of measure are used to define digital capacities and speeds. For measurements of a meter, see metric system. See binary values, NIST binary and long scale.
************************************** S P A C E ************************************** 10 to theBits or Bytes Power of: Kilo (K) Thousand 3 Mega (M) Million 6 Giga (G) Billion 9 Tera (T) Trillion 12 Bytes Peta (P) Quadrillion 15 Exa (E) Quintillion 18 Zetta (Z) Sextillion 21 Yotta (Y) Septillion 24 Bronto Octillion 27 Geop Nonillion 30 Storage Capacity Measured in: CPU word size bits Disk/SSD/USB drive bytes Memory (RAM) bytes **************************************** T I M E ***************************************Fractions of a second 10 to theSecond Power of: Millisecond (ms) Thousandth -3 Microsecond (µs) Millionth -6 Nanosecond (ns) Billionth -9 Picosecond (ps) Trillionth -12 Femtosecond (fs) Quadrillionth -15 Attosecond (as) Quintillionth -18 Zeptosecond (zs) Sextillionth -21 Yoctosecond (ys) Septillionth -24 Transmit/Transfer Measured in: Parallel bus/channel bytes/sec Parallel disk drive bytes/sec Memory (RAM) bytes/sec Cellular data plan bytes Serial bus/channel bits/sec Serial disk drive bits/sec Network & communications bits/sec Disk access time ms SSD access time µs RAM access time ns Machine cycle µs, ns Instruction execution µs, ns Transistor switching ns, ps, fs CPU Speed - Clock Cycles Per Second See Hertz. kilohertz (kHz) thousand megahertz (MHz) million gigahertz (GHz) billion terahertz (THz) trillion
speed of lightAll electromagnetic radiation, including light, radio transmission and electricity, travels at approximately 186,000 miles (300,000 kilometers) per second; more than seven times around the equator in one second. More precisely, the speed is 299,792,458 meters per second in a vacuum.
Never Fast Enough!
This inherent speed of Mother Nature is why computers work so fast. Within the tiny chip, electricity has to flow only a couple of millimeters, and, within an entire computer, only a few feet. Yet, as fast as that is, it is never fast enough. There is resistance in the lines, which slows down the current, and even though transistors switch in billionths of a second, scientific and multimedia applications are always exhausting the fastest computers. See software bloat.