There are approximately two billion children (persons under 18) in the
world. However, since Santa does not visit children of Muslim, Hindu,
Jewish or Buddhist religions (except maybe in Japan), this reduces the
workload for Christmas night to 15% of the total, or 378 million kids
(according to the population reference bureau). At an average rate of
3.5 children per household, that comes to 108 million homes, presuming
there is at least one good child in each. Santa has about 31 hours of
Christmas to work with, thanks to the different time zones and the
rotation of the earth, assuming he works east to west (which seems
logical). This comes out to 967.7 visits per second. This is to say that
for each Christian household with a good child, Santa has around
1/1000th of a second to park the sleigh, hop out, jump down the
chimney, fill the stocking, distribute the remaining presents under the
tree, eat whatever snacks have been left for him, get back up the chimney,
jump
into the sleigh and get onto the next house. Assuming that each of these
108 million stops is evenly distributed around the earth (which, of
course, we know to be false, but will accept for the purposes of our
calculations), we are now talking about 0.78 miles per household; a
total trip of 75.5 million miles, not counting bathroom stops or breaks.
This means Santa's sleigh is moving at 976 KM per second--3,000 times
the speed of sound. For purposes of comparison, the fastest man made
vehicle, the Ulysses space probe, moves at a poky 41.1 km per second,
and a conventional reindeer can run (at best) 22 km per hour. The
payload of the sleigh adds another interesting element. Assuming that
each child gets nothing more than a medium sized LEGO set (two pounds),
the sleigh is carrying over 500 thousand tons, not counting Santa
himself. On land, a conventional reindeer can pull no more than 145
kg. Even granting that the "flying" reindeer can pull 10 times the
normal amount, the job can't be done with eight or even nine of
them---Santa would need 360,000 of them. This increases the payload,
not counting the weight of the sleigh, another 54,000 tons, or roughly
seven times the weight of the Queen Elizabeth (the ship, not the monarch).
A mass of nearly 600,000 tons travelling at 975 km per second creates
enormous air resistance - this would heat up the reindeer in the same
fashion as a spacecraft re-entering the earth's atmosphere. The lead pair
of
reindeer would absorb 14.3 quintillion joules of energy per second each.
In
short, they would burst into flames almost instantaneously, subsequently
exposing each pair of reindeer behind them to the same fate while
creating deafening sonic booms in their wake. The entire reindeer team
would be vaporised within 4.26 thousandths of a second, or right about
the time Santa reached the fifth house on his trip. Not that it matters,
however, since Santa, as a result of accelerating from a dead stop to
975 km in .001 seconds, would be subjected to acceleration forces of
17,000 G's. A 130 kg Santa (which seems ludicrously slim considering
all the high calorie snacks he must have consumed over the years) would be
pinned to the back of the sleigh by 4,315,015 pounds of force,
instantly crushing his bones and organs and reducing him to a quivering
blob of pink goo. Therefore, if Santa is late to your place this year,spare a thought,he`s got a bit to do.

But then again Santa is magical,so physics don`t apply.