Aodhan Ite an Fhithich aodhan at
Mon Mar 27 17:15:03 PST 1995

Dia duit!

 [Replying to a message of "Mark Harris"  to All]


 "H> Firstly, (1) F = M * a -- that is, force = mass x acceleration (not
 "H> velocity).

 "H> Please recheck this. Using this equation if an object hits you at a
 "H> constant velocity (ie: a = 0) then it hits with no force. I find it
 "H> hard to believe that the non-accelerating piano at a constant 30 MPH
 "H> is going  to hit softer than the bottle rocket going from 0 MPH to
 "H> whatever. <<<<<

The equation *is* correct, however, your application of it is not.

A free-flying bolt is under going two forms of acceleration:  gravity trying
to pull it to the ground and drag trying to slow it down.  More germane,
however, is the fact that the bolt undergoes a negative acceleration when it
hits something.  The Kinetic Energy of the bolt [KE = M * (V ** 2)] is
transfered to the target (less some loss due to compression of the blunt). 
This transfer takes place over some period of time (let's call it Ti - time of
impact).  Thus, the acceration is the change in velocity over the time
required for that change [a = V / Ti] and equation (1) gives you the force of
the impact.

As someone once said, "I don't mind falling, it's that sudden stop at the

Feicfidh me' ari's thu',

Baron Aodhan Ite an Fhithich    aodhan at
Master of the Laurel            Lough na Dobharchu' BBS  1-713-338-2570
Dobharchu' Herald               "Your Information Roman Road"
mka David H. Brummel            1:106/22  180:11/22  762:2200/2
SCA Member 02245                Barony of Loch Soilleir, Ansteorra
plummety sable and argent on a sun of eight rays or a feather bendwise
sinister sable
No bird soars too high, if he soars with his own wings. - Blake

More information about the Ansteorra mailing list