Tracking the whole hammer

(See also the position plot with velocity vectors.)
This image tracks the downstroke of my hammer during a single blow to a piece of hot steel. Tracking begins as soon as the hammer begins appreciable downward movement and last about 175 milliseconds.

My hand grips the handle near its end. Notice the how the end of the handle moves in a nearly straight line during the early part of the blow, contrary to the intuitive sense that a hammer is "swung" in a sort of roundhouse blow.

Hammer flight path...

The hammer head's path is also nearly linear over more than a third of its flight. What are the forces that accelerate the head along this path? The center of gravity of the hammer is only slightly back of the center of gravity of the head and the only significant forces are those exerted by my hand and by gravity.

Hammer rebound

Hammer rebound...

See that during rebound I continue to pull the hammer toward myself, the direction of the force that was radial as the hammer descended. Then I push forward at the same time that I begin to lift the hammer.

(Note that the positions plotted here don't represent equal time intervals so you can't estimate acceleration from the distances between them.)

Updated 9 May 2000 -- Mike Spencer