The amount of energy delivered to the target by the hammer-blow is
equivalent to one half the mass of the head times the square of the
head's speed at the time of impact (E={mv^2 \over 2}). While the
energy delivered to the target increases linearly with mass, it
increases geometrically with the speed (see the effect of the handle,
below). High tech titanium heads are lighter and allow for longer
handles, thus increasing velocity and delivering more energy with
less arm fatigue than that of a steel head hammer of the same weight.
As hammers must be used in many circumstances, where the position of
the person using them cannot be taken for granted, trade-offs are
made for the sake of practicality. In areas where one has plenty of
room, a long handle with a heavy head (like a sledge hammer) can
deliver the maximum amount of energy to the target. But clearly, it's
unreasonable to use a sledge hammer to drive upholstery tacks. Thus,
the overall design has been modified repeatedly to achieve the
optimum utility in a wide variety of situations.
but hammers are already available in a variety of masses - from tack
hammers to sledge hammers.
Titanium allows a smaller mass while maintaining the same size
striking surface.
Do lighter traditional framing hammers have a smaller head? dunno