Yes, pit crews have to be very fast so that the racecar can get back in the race asap.
On race day, 43 active pit crews participate in the Nascar Sprint Cup Series. The drivers who did not make the race also have their own pit crews.
Safety for both the crews and drivers in the pit.
Everyday.
No. In 2011, Dale Jr. and Jeff Gordon swapped pit crews.
Usually there are as many pit crews in Formula One as the number of teams in the years racing calendar. Last year 2010 we had 12 teams and hence 12 pit crews. Each pit crew has more than 20 odd members and they all cater to the pit stop requirements of the 2 drivers of each team. This year 2011 too it would be the same.
Most of the time the pit crews do a 4 tire change and add a full tank of gas in about 12-14 seconds.
No a pit bike is a physically smaller version of a dirt bike. Originally built by pit crews from a child's minibike and used as a runabout in the pit area of a track, they are now commercially available and used in Mini Supermoto Racing.
If you are going to a NASCAR mechanic school, it is a good idea to go to some races while working on your degree. You can learn a lot about the industry. However, you should not be watching the cars as much as you are watching the pit crews. You will see how they do their jobs. This can help you to understand your classes and all of the things that you are learning.
The pit crew does not build engines. The teams engine department does this. The pit crew services the car during a race by fueling, changing tires and fixing the car so it can return to the race if the car gets damaged.
If you have a bottomless pit for a stomach...then pretty darn fast!
The fastest pit-stop performed during an official F1 event currently stands at 2.31 seconds set by Vodafone Mclaren Mercedes in the 2012 German Grand Prix at Hockenheim for Jenson Button during his second stop of the race.
It depends on what your weight is :)