Answer:
an instrument for measuring an electromotive force by balancing it against the potential difference produced by passing a known current through a known variable resistance.
 
        
             
        
        
        
A nebula is gas, dust, and other things that form and form some sort of clould like thing. It also looks cool because of the colors it produces. I'm sure you could do a web search to find more about it, I don't take astronomy hahaha
        
             
        
        
        
Answer:
c. may be accompanied by the sound of explosively expanding hot air, called thunder. 
Explanation:
Lightning is a discharge which is due to the reaction between oppositely charged charges in the clouds, or between clouds base and the Earth surface.
The motion of the cloud causes charging of clouds by friction, thus the reaction between opposite charges (jumping of charges from one cloud to another) in the cloud can lead to lightning. Also, oftentimes the bottom of a cloud is negatively charged so that this is attracted to the positive charge on the earth surface. Thus leading to a discharge called lightning.
Thus in the given question, the appropriate option is C. This implies that, lightning may be accompanied by the sound of explosively expanding hot air, called thunder. 
 
        
             
        
        
        
Answer:
( )=1913.31 N/m^2
)=1913.31 N/m^2
Explanation:
given:
 =0.85
=0.85
 =90 m/s
=90 m/s
γ∞=1.23 kg/m^3
solution:
since outside pressure is atm pressure vaccum can be defined by ( )
)
 =√2(
=√2( )/γ∞[
)/γ∞[ -1]
-1]
( )=1913.31 N/m^2
)=1913.31 N/m^2