It's used to measure the mass or weight of an object
Rarefraction.
Crest- tallest spot on transverse wave.
Trough- shortest point on transverse wave.
Compression - spot on a compressional wave where the waves are closer together.
Rarefraction - spot on a compressional wave where the waves are farther apart.
Answer:
dam/hydro power
Explanation:
estuary is the place where rivers meet the ocean, there are a lot of currents there (waves...) so it likely means thery use a dam or some sort of way of collecting electricity from the motion of the water there. many birds live in estuaries because of being able to find fish to feed from
Density can be any number, as long as it has the right units.
A unit of density has to be (a unit of mass) divided by (a unit of volume).
The most common one is gram/cm^3.
