What is speed?

2009-05-14T03:39:00.000-07:00

Speed is the rate of motion. It is the distance traveled per unit time denoted by the formula;

^v = ^d/_t

where:

v = speed

d = distance

t = time

Speed is a scalar quantity, meaning it has no element of direction. Velocity in contrast is a vector quantity. It has speed as its magnitude and an element of direction. An example of this is the travel of a hurricane. A hurricane has speed traveling in a certain direction.

Units of speed include:

meters per second, (symbol ms-1; m/s), the SI derived unit
kilometers per hour, (symbol km/h)
miles per hour, (symbol mph)
knots (nautical miles per hour, symbol kt); usually used on marine vessels
mach number, speed divided by the speed of sound
speed of light in vacuum (symbol c) is one of the natural units

c = 299,792,458 ms-1

Important conversions between units of speed include:

1 m/s = 3.6 km/h
1 mph = 1.609 km/h
1 knot = 1.852 km/h = 0.514 ms-1

Some known speeds :

Speed of a common snail = 0.001 ms-1; 0.004 km/h; 0.002 mph (1 millimeter per second).

A brisk walk = 1.7 ms-1; 6 km/h; 4 mph (5.5 feet per second).

Olympic sprinters (average speed over 100 metres) = 10 ms-1; 36 km/h; 22 mph.

Taipei 101 observatory elevator = 1010 m/min ; 16.7 ms-1 ; 60.6 km/h; 37.6 mph

Cruising speed of a Boeing 747-8 = 290 ms-1; 1050 km/h; 650 mph; (Mach 0.85)

The speed of sound in dry air at sea-level pressure and 20 °C (293 kelvin) = 343 ms-1 ≈ 1235 km/h ≈ 768 mph ( = Mach 1 by definition).

Official flight airspeed record = 980 ms-1; 3,530 km/h; 2,194 mph.

Escape velocity on Earth: 11.2 km/s

Space shuttle on re-entry = 7,800 ms-1; 28,000 km/h; 17,500 mph.

Average orbital speed of planet Earth = 29,783 ms-1; 107,218 km/h; 66,623 mph.

Speed of light in vacuum (symbol c) 299,792,458 ms-1 (exactly, by definition).

(Ref. Wikipedia)

Introduction

2008-10-20T00:22:00.000-07:00

The parsec ("parallax of one arcsecond", symbol pc) is a unit of length, equal to just over 30 trillion kilometres, or about 3.26 light years. The parsec is used in astronomy.

The parsec is defined as the length of the adjacent side of an imaginary right triangle in space. The two dimensions that this triangle is based on are the angle (which is defined as 1 arcsecond), and the opposite side (which is defined as 1 Astronomical Unit, which is the distance from the Earth to the sun). Using these two measurements, along with the rules of trigonometry, the length of the adjacent side (the parsec) can be found.(Wikipedia)

The term parsec is first used by Herbert Hall Turner in 1913 from an astronomical publication.

One parsec is approximately 3.262 light-years, that is, the distance traveled by light in 3.26 earth years.

The parsec is a unit of distance in space and when we mean distance, it is how far we traveled. Traveling would mean an account for speed.

And with that, this blog is born...

One Parsec

What is speed?

Introduction