Mid-ice
collisions
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There is a lot of
energy transferred in mid-ice collisions. Hockey players use body checks to try
and take the puck away from one another. An elastic collision is when two objects
collide all the kinetic energy is conserved. An inelastic collision, which we
see all the time when players collide, is when the energy becomes absorbed by
either object. Its similar to getting in a car wreck; when vehicles collide
with one another, the energy gets transferred into the frame and/or the
plastics and aluminum surrounding the vehicle. In professional hockey, the
players are travelling at speeds varying from 20 to 30 miles per hour and then
collide, with a purpose of course. In hockey most players grow up checking so
they know how to take and give hits. But sometimes they catch unexpected ones
and it can be very detrimental to their health and/or career. A video of a
collision that makes me cringe, http://www.youtube.com/watch?v=cIXcGOr4-04.
All of the energy between two objects or players must be conserved. There are
many factors which go in to collisions on the ice, some of them being:
o
The speed or
velocity at which they are moving.
o
The mass of
players making contact.
o
The angle at
which they hit one another.
o
Where the player
made contact.
o
The amount of
muscle or padding that one player uses.
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An inelastic
collision can be more visible in hockey fights. Every player who has had a
broken nose due to a fight knows what I mean. The kinetic energy was not
totally conserved and some energy went into shearing bone. This type of
collision is not a perfect inelastic collision however; in a perfect inelastic
collision two objects would collide and travel together because they become
entangled. Instead some of the energy is absorbed in the form of internal
energy. Through a series of calculations and the use of multiple equations one
can come up with the amount of energy transferred from one body to another. In
the reference page under mid-ice collisions it can be seen that the author had
gone through these series of calculations and calculated that a 240 pound man
(travelling four meters per second) hitting a 189 pound man (stationary)
transferred, not created, but transferred 0.36 kilojoules, which could power a 60
watt light bulb for six seconds. The energy transferred would send both people
at a speed together of 2.3 meters per second.
o
The mathematical
view of this is the conservation of momentum law that applies to collisions
like these is (where m is the mass of the object (player), v is the
velocity of that specific object (player) and i symbolizes the initial velocity,
f symbolizes final velocity) :
M1i V1i+ M2i V2i= M1f V1f+ M2f
V2f