Short answers, pulled from the story.
The earliest known hammers date to 3.3 million years ago based on a 2012 excavation near Kenya's Lake Turkana. These shaped stones lacked handles and were used by Sonia Harmand and Jason Lewis from Stony Brook University to strike wood, bone, or other stones.
Modern hammer heads typically consist of steel heat-treated for hardness or high-tech titanium that reduces recoil to about 3 percent compared to 30 percent for steel. Specialized designs also use aluminum or beryllium copper to create non-sparking tools for coal mines and petroleum refineries.
Kinetic energy equals half the mass of the head times the square of its speed at impact, meaning energy increases linearly with mass but quadratically with velocity. Dead blow hammers fill hollow heads with sand or lead shot to absorb bounce while gravity accelerates downward strokes to maximize force.
Blacksmiths employ rounding hammers to draw out metal or smooth surface marks while masons utilize splitting mauls to divide large blocks of stone into smaller pieces. Geologists use rock picks to break up stones during fieldwork and railway track keying hammers assist engineers working on steam locomotives.
The addition of wooden handles appeared around 30,000 BCE during the Paleolithic Stone Age when strips of leather or animal sinew attached stones to sticks. This innovation reduced accidents and gave users greater leverage over their environment compared to handle-less predecessors.