I - ok. Czechoslovakia is officially taken.
Answer:
MATERIAL MEDIUM
Explanation:
Wave is a disturbance that travels through a medium and transfer energy from one point to another without causing any permanent displacement of the medium itself. The two forms of wave are the mechanical wave and the electromagnetic waves.
Mechanical wave is a wave with requires MATERIAL MEDIUM for its propagation. This means that before wave can be propagated at times, material medium is needed e.g a ripple tank. A ripple tank is a mechanical device that generates waves using an instrument called stroboscope attached to it. This kind of wave requires an external source before it can propagate compared to electromagnetic waves that does not require material medium for its propagation.
Answer:
h=17357.9m
Explanation:
The atmospheric pressure is just related to the weight of an arbitrary column of gas in the atmosphere above a given area. So, if you are higher in the atmosphere less gass will be over you, which means you are bearing less gas and the pressure is less.
To calculate this, you need to use the barometric formula:

Where R is the gas constant, M the molar mass of the gas, g the acceleration of gravity, T the temperature and h the height.
Furthermore, the specific gas constant is defined by:

Therefore yo can write the barometric formula as:

at the surface of the planet (h =0) the pressure is ![P_0[\tex]. The pressure at the height requested is half of that:[tex]P=\frac{P_0}{2}](https://tex.z-dn.net/?f=P_0%5B%5Ctex%5D.%20The%20pressure%20at%20the%20height%20requested%20is%20half%20of%20that%3A%3C%2Fp%3E%3Cp%3E%5Btex%5DP%3D%5Cfrac%7BP_0%7D%7B2%7D)
applying to the previuos equation:

solving for h:
h=17357.9m