Answer:
Solids
Explanation:
Sound travels fastest through solids. This is because molecules in a solid medium are much closer together than those in a liquid or gas, allowing sound waves to travel more quickly through it. In fact, sound waves travel over 17 times faster through steel than through air.
True. Because you can touch it and it's physically real.
Answer:
Post indicator valve
Explanation:
Post Indicator Valves are commonly used to control the water flow of sprinkler systems used in public and private buildings, warehouses, and factories for fire suppression. PIVs control water flow from the public system into the building's fire suppression system.
To solve this problem it is necessary to apply the concepts related to hydrostatic pressure or pressure due to a fluid.
Mathematically this pressure is given under the formula
Where,
= Density
h = Height
g = Gravitational acceleration
Rearranging in terms of g
our values are given as
Replacing we have
Therefore the gravitational acceleration on the planet's surface is 
(Almost the gravity of the Earth)
