[TheForge] Re: uri hammer

[Mike Spencer]

> Hmm.  Looking at the web page, I wonder if you ever figured
> out the energy imparted to the hot iron by the hammer head?

Well, I have a little trouble with the computations. [1]  But as a
first approximation, the kinetic energy of the hammer head is:

    1/2 X mass-of-hammer X velocity-of-hammer X velocity-of-hammer

    1/2 m v^2

If the hammer head stops dead with no rebound, then there's zero
kinetic energy so all the kinetic energy of the hammer must have been
converted into work in deforming the the iron and is eventually
dissipated internally as heat.  If there's rebound, that kinetic energy
has to be subtracted from the original KE to get how much went into
the iron.

Rebound is hard to measure with a hand hammer.  And the above ignores
all the other possible variables such as energy absorbed by the anvil
and stump/stand, energy dissipated as sound, etc.

Those pics on the web page were done with hot iron.  We did some
others with a piece of lead and with a piece of cold steel at faster
frame rate.  I haven't gone over those carefully but intuitively,
there was less rebound with the lead and, of course, a great deal with
cold iron.

Thinking about this stuff is for the winter when the shop is cold, the
snow deep and the house warm.  Maybe this winter.  I finally found
some manuals for Maple V and mean to play with it when the weather is
nasty.


- Mike

[1] "...a little trouble with the computations."  Tedious and OT.  I
    don't have trouble with the usual, textbook, frictionless billiard
    ball or ballistic pendulum examples of conservation of momentum.
    But in the case of hammering on an anvil, I can't quite figure out
    how to do the computations when the "system" consists (1) a hammer
    of mass m and velocity v colliding with (2) the earth of mass
    5.9736e24 kg and velocity 0, of which latter a little piece (the
    hot iron) is (almost) completely inelastic.  I need to put my feet
    up, read some hard stuff (hard for me, anyhow) and scribble,
    scribble, scribble.

-- 
Michael Spencer                  Nova Scotia, Canada       .~. 
                                                           /V\ 
mspencer at tallships.ca                                     /( )\
http://home.tallships.ca/mspencer/                        ^^-^^

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