Fall of a meteorite
Analyze the propagation of seismic waves with FizziQ
Autor:
Título 4
Learning objectives :
This activity allows students to understand the propagation of seismic waves and the transfer of energy during an impact. It makes the link between an astronomical phenomenon and its physical measurement.
Concepts covered
Seismic waves; Energy transfer; Potential and kinetic energy; Propagation of mechanical waves; Impacts and cratering
What students will do :
The student simulates the impact of a meteorite by dropping balls of different masses and different heights on various surfaces. By using the FizziQ accelerometer to measure the vibrations generated by these impacts, the student analyzes how the energy of the impact propagates in the form of waves and how the different parameters influence the intensity of the seismic waves.
What is required :
Smartphone with the FizziQ application; Balls of different masses and sizes; Surfaces of different compositions (wood, metal, sand, etc.); Ruler or tape measure to measure the height of fall; Salad bowl filled with sand
Scientific background :
A smartphone's accelerometer can detect very low amplitude vibrations (down to 0.01 m/s²) at a high sampling rate (>100 Hz), making it ideal for this experiment. When a ball falls, its potential energy (Ep = mgh) is converted into kinetic energy (Ec = ½mv²) just before impact. During the collision, this energy is partially transferred to the surface in the form of mechanical waves which propagate through the medium. These waves are similar to the seismic waves produced during the impact of a meteorite, but on a much smaller scale. The amplitude of the measured vibrations depends on several factors: the mass of the ball (m), the height of fall (h), and the properties of the material (rigidity, elasticity, density). The formation of craters in sand also follows physical laws established by studies of meteorite impacts: the diameter of the crater is proportional to the cubic root of the impact energy (D ∝E^(1/3)). This experiment also illustrates why seismometers are used to detect meteorite impacts on other celestial bodies, such as Mars where the Perseverance rover is equipped with similar instruments.