physucks is phun!!

see jimithy's blog (to the right) and read his post about exercise/lack of/gaining weight for the winter months. he says "If I get fat, who cares, more m1v1 for the ski slopes!". i was asked to explain, so here, bitches:

what is m1v1 you ask??

DAMN YOU AND YOUR OFFSPRING FOR NOT KNOWING!!!!

m1v1 is a referrence the conservation of momentum, which is an extension from Newtons III'd law (my favorite), which is that forces are equal and opposite.... for every action, there is an equal and opposite reaction.

simply stated, in a collision of two objects, the TOTAL momentum for both objects before and after the collision is the same, save for losses due to friction etc. think billiards. one ball hits another. ball one stops dead in its tracks while ball two hauls ass into the pocket at roughly the same speed as ball one was going before the collision. it is not exactly the same speed because the collision between the two balls is not perfectly elastic, though it is close.

the equation changes form slightly depending on the type of collision:

elastic collision:


head on collision (one dimension):

and


inelastic collision:


this equation can be taken form its simple form above, all the way to a complex integral form. this, for example, is the integral form modeling the unsteady open-channel flow of water:



it defines the time rate of change of momentum per unit length as the sum of the net downstream forces and the net efflux of momentum. simply stated, how much momentum does a unit of water gain or lose by moving through an open channel*.

now back to the topic at hand.... while the modeling of the collision of two balls is not equivalent to skiing, as shown above, the basic principal can be streched and formed into a complex formula that can model jimithy's momentum whilst skiing. simply stated, the more he weighs, the faster he can go down the slope. HOWEVER, this is only true if his skis are properly waxed. the force of friction on his skis will also increase if he weighs more (more normal force), but if the skis are waxed well, the loses due to increased friction can be reduced.

i remember racing my father down the slope as a kid and i could never win. i was 125 pounds, and my dad was probably 225. he would just glide down the hill as i tucked, trying to gain speed (lessening my air resistance). this is not to say that things that weigh more fall faster, however. a ball of tin foil falls at the same speed as a ball of lead. in the case of skiing though, all the forces in action emphasize differences in weight. i never won, mostly because he weighed more, but also because was being a dick and wouldn't let me. yet another character builder....

in any event i finish this post with the words of my favorite teacher in hich school: "Put that in your pipe and smoke it!"


*open channel.... i.e. - a trough, river, or equivalent that has only three wet surfaces as opposed to a closed system, i.e. - pipe.