The density value 3.291 g/ml (gram / milliliter) in words is "three point two nine one g/ml (gram / milliliter)". 
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Answer:
Motors commonly contain a "commutator" which allows a magnetic field due to a loop of wire to always be in a say "clockwise or counterclockwise" direction even tho the loop of wire is rotating.
That means that magnetic field due to the surrounding magnets is always in the same direction, but the magnetic field due to the rotating   loop of wire is continually changing so that it will always oppose the surrounding field which remains in a constant direction.
This is most easily seen in a "DC - direct current motor".
 
        
             
        
        
        
Explanation:
A simple harmonic oscillation is an oscillator that is neither driven nor damped.
 
        
             
        
        
        
Gas stations or sewage treatment facility