it is called a tricycle

there are many types of languages in which it can be pronounced, in India it is called as Auto Rickshaw.

Don't really understand what you're saying here. The saddle doesn't do anything for the parts of the bike usually related to friction - ie wheel bearings, drive train etc.

"All" that a saddle do is offer a place that can support the butt and offer some leverage for the thighs, which helps with controlling the bike.

One of the advantages of SPD Pedals is that it makes pedaling more efficient on a bike. Another of the advantages is that it makes climbing uphill more easy.

Age doesn't matter, size does. Do a net seach for "bicycle size fitting" and you'll get plenty of hits.

Some really crude ones based only on total height. some more sophisticated that take body proportions into account.

All I can dig up is that it was patented by Frederick W. Schwinn, patented June 5, 1945
It is said that tandem bikes were invented by Mikael Pederson in the 19th century who patented his tandem version of his Pederson bicycle around 1898.
In a tandem, two or more riders sit behind each other. In 1898, in England, Danish inventor Mikael Pedersen developed a two-rider tandem version of his Pedersen bicycle. This was the first tandem.

Bicycles as a rule don't end up being valuable collectibles. Your best bet is to look for similar bikes on ebay, craigslist and suchlike, and see what they are selling for.

about up to 12 miles per hour but you should see the world record

Completely depends on you and the extent of the injury. When I broke my ankle in November 1989 (hit by a car), I still rode every day, even though I could not stand on it for 6 weeks. The nearly impossible part was clipping in, so I switched around and unclipped the right foot at red lights...made more difficult by the road tilting down to the right in my area of the country and starting up when the light turns green without putting any downward pressure on the broken foot. Interestingly, I can say that you will go 2mph faster with your foot clipped in (rather than left out) even with no pressure, merely because of the weight of your leg and the smoothing effect of more even power applied to the pedals.

About 5 minutes at a comfortable pace.
It depends on how fast you pedal.

It is possible to put a 6 speed back wheel on a 21 gear bicycle but you will never be able to use more than the 6 gear allowed by that cassette sprocket.

The best way to take advantage of the 21 gear bicycle is to change that 6 speed cassette sprocket and replace it by a 7 speed cassette sprocket. This way you will keep that back wheel and also be able to use all 21 gears of your bike.

Becaks aren't unicycles at all. Unis only have one wheel, becaks have three.

A becak is a tricycle cargo bike, usually in what's called a "tadpole"(two wheel forward) configuration.

For just riding back and forth to school or the store, just fine.

If you're planning on doing anything more risky than just riding it, invest in something a little more pricy.

Big Wheel tricycles for kids can be bought from Walmart, Target, Sears, The Bay, Toys R Us, Amazon, California toys, Urban Tyke,eBay, Kijiji and Craigslist.

the rider uses energy to do work going up the mountain this energy changes into kinetic energy on the way down

Kids heads are heavier in proportion to their overall body weight than an adult's, and kids are overall more likely to fall than adults. Both good reasons for them to use extra protection.

it would depend on whither you are riding on a mountain bike or something that wont be doing stunts or a bmx or dmr. for mountain bike it probably will not matter whither it is big or not however for bmx or dmr it would be a good idea to have a smaller one as when at skate parks eg. you where going to drop into a bowl that is quite steep if you have a big on then the chances are it is going to hit the coping (top of edge) and maybe fall off. also if you are thinking of getting a smaller sprocket you will need to get a smaller cassette but don't guess how big the cassette should be for a sprocket just take it to a bike shop and they should be able to tell you. for a smaller sprocket i would recommend a 25t to 30t,, the 25t will have to have about an 8 or 9 tooth cassette. hope all of this helps took me a while to type out anyway :P!!

The dimensions of the tire is written on the sidewall of the tire. Make a note of these, then just buy an inner tube with the same dimension. You can go a bit narrower than recommended but the wheel diameter needs to be of the right size.

There is no reason not to ride a bike if you are heavy. However, make certain that you do not exceed the weight limits of the bike. Special heavy duty bikes may be a solution to the problem.

frame tubes are constructed from solid blocks of steel that are pierced and "drawn" into tubes through several stages. These are usually superior to seamed tubes, which are made by drawing flat steel strip stock, wrapping it into a tube, and welding it together along the length of the tube. Seamless tubes may then be further manipulated to increase their strength and decrease their weight by butting, or altering the thickness of the tube walls. Butting involves increasing the thickness of the walls at the joints, or ends of the tube, where the most stress is delivered, and thinning the walls at the center of the tube, where there is relatively little stress. Butted tubing also improves the resiliency of the frame. Butted tubes may be single-butted, with one end thicker; double-butted, with both ends thicker than the center; triple-butted, with different thicknesses at either end; and quad-butted, similar to a triple, but with the center thinning towards the middle. Constant thickness tubes, however, are also appropriate for certain bikes.

The tubes are assembled into a frame by hand-brazing or welding by machine, the former being a more labor-intensive process and therefore more expensive. Composites may be joined with strong glue or plastic binders. The components are generally manufactured by machine and may be attached to the frame by hand or machine. Final adjustments are made by skilled bicycle builders.

Really depends on what kind of bike you're looking at. A nice road bike can be 16 lbs, while a DH MTB can be 40 lbs.

The parts to build a bare-boned fixed gear you need:

1. A bicycle frame with non-vertical rear drop outs. Google "vertical drop outs" and then "horizontal drop outs." Horizontal dropouts are necessary to tension a chain.

2. A rear wheel with a track hub. These are threaded so that a special fixed gear cog threads on, and then a lock ring threads on in the opposite direction to keep the cog from coming undone while you are riding.

3. A cog and lock ring as described above

4. A bottom bracket and/or crank which will allow you to make a straight chain line from the cog to the front chain ring. This is important both for efficiency and safety reasons. By moving the chain ring closer/farther away from the bottom bracket it may be possible to make the chain go in a straight line from the cog to the chain ring. However, it may also be necessary to get a shorter bottom bracket spindle to bring the cranks and chain ring closer to the frame.

5. The other parts. Namely, a seat, chain, chain rings, seat post, stem, headset, handlebars, pedals, cranks, front wheel, inner tubes, tires, etc.

Riding without brakes is unnecessarily hard on your knees and I'd recommend against it. AND MAKE SURE YOUR LOCK RING IS TIGHTENED DOWN!

Tour de France