Answer:
D ko alam pasensya ka na ha
To solve this problem it is necessary to apply the concepts related to Hooke's Law as well as Newton's second law.
By definition we know that Newton's second law is defined as

m = mass
a = Acceleration
By Hooke's law force is described as

Here,
k = Gravitational constant
x = Displacement
To develop this problem it is necessary to consider the two cases that give us concerning the elongation of the body.
The force to keep in balance must be preserved, so the force by the weight stipulated in Newton's second law and the force by Hooke's elongation are equal, so

So for state 1 we have that with 0.2kg there is an elongation of 9.5cm


For state 2 we have that with 1Kg there is an elongation of 12cm


We have two equations with two unknowns therefore solving for both,


In this way converting the units,


Therefore the spring constant is 313.6N/m
Infra sounds are sounds with frequencies below 20 Hz.The popular concept that infra sounds are in audible holds false
Explanation:
- Some example of Infrasounds are- some animals such as whales, elephants and giraffes which communicate with each other using infrasound over long distances.
- Various natural phenomenon such as Avalanches, volcanoes, earthquakes, ocean waves, water falls and meteors also generate infrasonic waves
- Infrasound, is sound that is lower in frequency than 20 Hz or cycles per second.
- Even the human body can generate mechanical vibrations at very low frequencies, which are known as the infrasonic waves. Such low-frequency vibrations/infrasonic waves are produced by physiological processes—such as heartbeats, respiratory movements, blood flow in vessels, and other processes.