Chapter 10 & 11 Elasticity, Oscillations, Waves, and Sound   Mechanical Waves A progressive or traveling wave is a self-sustaining disturbance of a medium that propagates from one region to another, carrying energy and momentum.   Longitudinal Wave – the sustaining medium is displaced parallel to the direction of propagation.   Transverse Wave – the sustaining medium is displaced perpendicular to the direction of propagation.     Period – the time it takes for a wave to go through one complete oscillation. Frequency – the number of complete oscillations the wave makes in a second. Wavelength – the spatial distance over which the wave makes one complete oscillation.   Speed of any progressive periodic wave: (16)   Problem 16 Sound waves travel in air with a speed of 343 m/s. The lowest frequency sound we can hear is 20.0 Hz; the highest frequency is 20.0 kHz. Find the wavelength of sound for frequencies of 20.0 Hz and 20.0 kHz.   Solution: Solve equation (16) for the wavelength:   Transverse Waves: Strings Speed of a transverse wave in a string: (17) where is the tension in the string and m/L is the mass per unit length.   Example 17 A 5.0 m length of rope, with a mass of 0.52 kg, is pulled taut with a tension of 46 N. Find the speed of waves on the rope.   Solution: Use equation (17) to find the speed of the wave:   Example 18 A 12 m rope is pulled tight with a tension of 92 N. When one end of the rope is given a "thunk" it takes 0.45 s for the disturbance to propagate to the other end. What is the mass of the rope?   Solution: Calculate the speed of the wave: Use equation (17) to solve for the mass: Sound Part 2