VI.5. Summary - Mechanical waves, sound.
VI.5.1 Mechanical waves, sound.
📚 Summary - Mechanical waves, sound.
VI.5.2. Worksheet - Mechanical waves.
📋 Worksheet - Mechanical waves.
1. Complete the following statements:
a) The mechanical oscillation represents the ................. movement of a body with respect to a position of equilibrium, repeated .............
b) Mechanical wave is the phenomenon of propagation of an .............. through a substance accompanied by ............ transport.
c) The sound changes its ................ depending on the environment traversed.
d) The supersonic body has a speed higher than the speed ...........................
Solution:
a) The mechanical oscillation represents the symmetrical movement of a body with respect to a position of equilibrium, repeated periodically.
b) Mechanical wave is the phenomenon of propagation of an oscillation through a substance accompanied by energy transport.
c) The sound changes its speed depending on the environment traversed.
d) The supersonic body has a speed higher than the speed of sound through the air.
2. Answer true or false at the following statements:
a) Transverse waves propagate with the perturbation perpendicular to the direction of oscillation of the environment particles.
b) The sound timbre allows the identification of the sound intensity.
c) The sonar is an application of infra-sound reflection.
d) Sound intensity is measured in Hertz.
Solution:
a) Transverse waves propagate with the perturbation perpendicular to the direction of oscillation of the environment particles. -True
b) The sound timbre allows the identification of the sound intensity. -False
c) The sonar is an application of infra-sound reflection. -False
d) Sound intensity is measured in Hertz. –False
3. Why don't we always hear the echo of the sounds we make?
Solution:
The human ear is impressed (occupied) with a sound for 0.1 s. If the obstacle is too close to us, the reflected sound reaches our ear too quickly (in less than 0.1 s) and we do not hear it as an echo. To hear the echo of a sound, the obstacle must be at a minimum distance of 17 m from us.
4. Characterizes ultrasound.
Solution:
Ultrasound has a frequency of more than 20000 Hz and we do not hear it. Bats, dolphins, dogs, cats, moths emit ultrasound.
5. Determine the speed of an airplane in km / h knowing that it has a speed of 4 Mach.
Solution:
We transform from Mach to m/s and then to km/h:
6. A guitar string emits 123 Hz sound. Find out the oscillation period of the string and the wavelength of the oscillation of the guitar string.
Solution:
We write down the data of the problem and turn it into SI:
Oscillation frequency = υ = 123 Hz (1/s)
We apply the period formula and then calculate the wavelength of the oscillation:
