Piano Strings         A piano’s strings are stretched out over its cast iron frame, and create sound once they are struck by felt covered hammers. These hammers are triggered by the keys on the piano’s keyboard. Cristofori created the “escapement” action of the hammers, which allowed the hammers to drop away from the string instantly as to not disrupt the vibrations. Going from bass to treble, the size of the hammers increase.         The notes on a piano are controlled by these individual strings or in sets of 2 to 3 which are made of high-tensile steel wire. The strings create a vibration at a specific frequency which is determined by the length, diameter, tension, and density of the wire.         Newton’s third law of motion can be seen in the way a player will press down on a key; for every action there is an equal and opposite reaction. The force you apply on the keys by pressing down on them will be equal to the force of the hammers hitting the string.          At the point of collision between the hammer and the string, the string becomes deformed and creates two waves on the string which travel in opposite directions. The waves become a pulse and “bounce back” once reaching the rigid support. This causes the waves to become inverted, which is important in restoring the string back to equilibrium.                                     https://www.speech.kth.se/music/5_lectures/introd/introd.html                                 http://www.zainea.com/piano%20sound.htm         A transverse wave travels through the string as a displacement perpendicular to the propagation of the waves.                                                             http://dev.physicslab.org/document.aspx?doctype=3&filename=wavessound_introductionwaves.xml