9 Sep

Hi there,
Have you ever observed how your father or other family drive their car? Look at his speedometer carefully !!!! say the average speed is about 80 km per hour. How about you? can you drive a car or ride a motorbike or a bikecycle??

For human beings, an average walking speed is about 3 mph (~5 km/h, 1.39m/s),
The speed of long distance jogging for average persons is about 6 mph (~10 km/h, 2.7 m/s).
Top athletic sprinters can run at 23.03 mph (~36.85 km/h, 10.24 m/s) within a short distance such as a 200 meters dash.
Cycling can average 12 mph (~20 km/h, 5.56 m/s)
Car can average 65 mph (~104 km/h, 28.9 m/s ) on highway
The hightest speed of MotoGP recorded 349,288 km/h, by Dani Pedrosa riding on Honda RC212V in Mugello, 2009.

The TGV (Train à Grande Vitesse, French for “High-Speed Train”) holds a series of world speed records achieved by SNCF, the French national railway, and its industrial partners. The high speed trials are intended to expand the limits of high speed rail technology, increasing speed and comfort without compromising safety. The current TGV world speed record is 574.8 km/h (357.2 mph), achieved on 3 April 2007 on the new LGV Est.

The speed of sound varies depending on altitude, temperature and the medium through which it travels. For example, at sea level in a standard atmosphere, at a temperature of 59-degrees Fahrenheit (15 Celsius), sound travels 761 miles per hour (1,225 km/h). At a temperature of 32-degrees Fahrenheit (0 Celsius) the speed of sound drops to 742 mph (1,194 km/h). In altitudes above sea ( http://www.wisegeek.com/what-is-the-speed-of-sound.htm)

It is sometimes objected that “they said no-one would ever go faster than sound and they were wrong. Now they say no-one will ever go faster than light…” Actually it is probably not true that anybody said it was impossible to go faster than sound. It was known that rifle bullets go faster than sound long before an aircraft did

let see the speed of concorde, Air France
Over sea the average cruising speed is Mach 2.02 (about 1,482 MPH). I believe your question is actually what is the fastest this jet can go. That answer is Mach 2.2 (1,614 MPH). One example of how fast it can cross the Atlantic is it once made a flight from Miami to London in 3 hours and 47 minutes (that is over 4,000 nautical miles). Unfortunately this jet is no longer in service.

I forget to tell you ….what is Mach?????
Mach number (Ma or M) (generally play /ˈmɑːk/, sometimes /ˈmɑːx/ or /ˈmæk/) is the speed of an object moving through air, or any other fluid substance, divided by the speed of sound as it is in that substance for its particular physical conditions, including those of temperature and pressure. It is commonly used to represent the speed of an object when it is traveling close to or above the speed of sound (http://en.wikipedia.org/wiki/Mach_number)

Thus Human can create a moving object exceeding the speed of the sound….But Can his creation even can go faster than the speed of the light ???????

The truth is that some engineers once said that controlled flight faster than sound might be impossible, and they were wrong about that. FTL travel is a very different matter. It was inevitable that someone would one day succeed in flying faster than sound, once technology got around the problems. It is not inevitable that one day technology will enable us to go faster than light. Relativity has a lot to say about this. When we discuss moving faster than the speed of light, we are really talking about exceeding the speed of light in vacuum c (299,792,458 m/s). The Cherenkov effect is thus not considered to be a real example of FTL travel.

WHAT IS THE SPEED ??? distance moved (D) per unit of Time (T)
Speed is the rate of motion, or the rate of change of position. It is expressed as distance moved (d) per unit of time(t). Speed is a scalar quantity with dimensions distance/time. Speed is measured in the same physical units of measurement as velocity, but does not contain an element of direction. Speed is thus the magnitude component of velocity. Velocity contains both the magnitude and direction components.

1. S = D/t
2. D = S*t
3. t = D/s

to remember its formula, just remember S as km/hour or use triangle helper in our previous lecture about density

What is acceration ???
To accelerate an object is to change its velocity, which is accomplished by altering either its speed or direction (like in case of uniform circular motion) in relation to time. Acceleration can have positive and negative values. Any time that the sign (+ or -) of the acceleration is the same as the sign of the velocity, the object will speed up. If the signs are opposite, the object will slow down. Acceleration is a vector quantity. When either velocity or direction changes, there is acceleration (or deceleration). To accelerate an object requires the application of a force.

Using a distance formula
Do you know that oceanographers use sonar to find the depth of the ocean ? they use equipment that enable to measure the time it take from the ocean surface to the bottom floor. in the sea sound travel a bit slower at 1460 m in a second.


1. on january 23, 1969, piccard and Walsh desecended to the ocean floor of the marianas trench in a special diving sphere. It took 7.4s for the sound to reach the sphere from the surface. How deep was the diving sphere?
2. Sound travels through sea water at a rate of 1460 m/s. How far would sound travel in the sea water in 2.7 seconds?

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