|MLA Citation:||Bloomfield, Louis A. "Question 163"|
How Everything Works 20 Jan 2018. 20 Jan 2018 <http://howeverythingworks.org/print1.php?QNum=163>.
But while the piston rebounds gently from a cushion of air at the top of the cylinder, it collides suddenly with a metal bar at the bottom of the cylinder. That metal bar is the top end of the drill bit that the jackhammer uses to cut into pavement. Each time the piston moves downward, it pounds the drill bit a little farther into the pavement. The enormous force that pushes the bit into cement comes from the enormous force needed to stop the descending piston and to accelerate it upward. The drill bit pushes up on the piston very hard and the piston pushes down on the drill bit very hard. These two forces are equal and opposite, as they must be (Newton's third law of motion.) The piston ends up moving upward and the drill bit ends up moving downward.