If you buy a car from a dealership you must be 19 so you can sign by yourself. Legal age to sign is 19. That might not go for some others like personal sellers or trades and etc. If you are asking minimum age for buying a car, it doesn't matter. Cars are property just like a stick of gum is.
The speed of the tips of the windmill blades should be about 5 times the speed of the wind. For a 10 m/s wind (about 20 mph, more or less), the tips move at 50 m/s. If the windmill has a large diameter, then 20 RPM is adequate, but if the diameter is small, a high RPM is required.he tip speed of the windmill blades is typically 5 times the wind speed. That is, in a ten-mph wind, the tip of the blades moves at 50 mph. (Think of the neighborhood kids getting into mischief.). 4. Ideally, you should have two or three blades.
View full size image. One of the fastest-growing sources of energy in the world, wind turbines generate electricity without emitting greenhouse gases into the environment (unlike fossil fuels). These modern-day windmills convert mechanical energy from the wind into electrical power. Most wind turbines have three main parts: the tower (the long stem that connects to the ground); the blades, which connect to a central hub (the rotor); and the nacelle (a box behind the blades that contains the generator).