Answer:
The momentum would be doubled
Explanation:
The magnitude of the momentum of the freight train is given by:

where
m is the mass of the train
v is its speed
In this problem, we have that the speed of the train is unchanged, while the mass of the train is doubled:

therefore, the new momentum is

so, the momentum has also doubled.
 
        
             
        
        
        
30x30=900
The answer is 900 meters after 30 seconds
 
        
             
        
        
        
Answer:
D
Explanation:
Political scientists use political models to describe the political climate, which is an aggregate mood or opinion of a political society at a point in time.
 
        
                    
             
        
        
        
Metal
Explanation:
semiconductors are materials which have a conductivity between conductors (generally metals)
 
        
             
        
        
        
According to periodic trends in the periodic table, the atomic radius decreases from left to right. 
In period three, the element with the smallest atomic radius would be the element in the rightmost area. Protons increase as it goes to the right, which would mean they pull in electrons closer which decreases the size. 
So in period 3, the element with the smallest atomic radius is Argon (Ar).