This requires a slightly elaborate solution and good wording is key to comprehending the solution. The following has been taken from http://www.scientificpsychic.com/mind/balls1.html 

Label the balls from 1 to 12 to identify them.
Weigh 1, 2, 3, 4 against 5, 6, 7, 8:

1. If they balance, 9, 10, 11, 12 contain the odd ball.
   Weigh 6, 7, 8 against 9, 10, 11.
   1. If they balance, 12 is the odd ball. Weigh 12 against any other ball to discover whether it is heavy or light.
   2. If 9, 10, 11 are heavy, they contain an odd heavy ball. Weigh 9 against 10. If they balance, 11 is the odd heavy ball, otherwise the heavier of 9 and 10 is the odd ball.
   3. If 9, 10, 11 are light, we use the same procedure to reach the same conclusion for the odd light ball.
      
2. If 5, 6, 7, 8 are heavy, either they contain an odd heavy ball or 1, 2, 3, 4 contain an odd light ball.
   Weigh 1, 2, 5 against 3, 6, 10.
   1. If they balance, the odd ball is 4 (light) or 7 or 8 (heavy). Weigh 7 against 8. If they balance 4 is light, otherwise the heavier of 7 and 8 is the odd heavy ball.
   2. If 3, 6, 10 are heavy, the odd ball can be 6 (heavy) or 1 or 2 (light). Weigh 1 against 2. If they balance 6 is heavy, otherwise the lighter of 1 and 2 is the odd light ball.
   3. If 3, 6, 10 are light, the odd ball is 3 and light or 5 and heavy. We thus weigh 3 against 10. If they balance, 5 is heavy, otherwise 3 is light.
3. If 5, 6, 7, 8 are light we use a similar procedure to that in II.

Hope, this was clear and sufficiently detailed.

Walking is a continuous process of transiting from stable position to falling forward and gaining stability again. Work done by friction is 0, since the point of contact is stationary. The work done by the man's leg muscles is positive, since the rear leg is stopped by friction from sliding, and acts as a temporary support, while the front leg swings forward (facilitated by the leg muscles) and then the whole body moves to the stable position ahead.

Form perfect squares, and you'll get a standard integral form

NASA is an organization, dude. You do space research there

ANd yes, you can apply, just go through the required qualifications and experience on their website: Search NASA on google

2^1 = 2

2^2 = 4

2^3 = 8

2^4 = 16

2^5 = 32 ..last digit is 2 again

so , the last digits repeat after every 4 powers of 2.

2009 = 4x502  + 1

So the digit will be the 1st one in this repeating group.. ie. 2

 All the nerve impulses in our body are actually minute bursts of electric current. So, for people whose hearts stop responding or lose control on their nervous system, for example, an electric shock of low intensity can, at times, help restore functionality.

 No, range of f(x) is (-infinity, 1)

 yeah, but start by browsing through the NASA website and see the recruiting process and requirements

just put 2 adjacent sides of the room, along which the fly will travel, flat together as a rectangle.

The diagonal of this rectangle then could be, depending on the position of the fly, sqrt[(3+4)^2 + 5^2] or sqrt[3^2 + (4+5)^2] or sqrt[4^2 + (3+5)^2]

These respectively are equal to sqrt(74), sqrt(90) and sqrt(80)

So the shortest is sqrt(74) m