Answer:
d = 69 .57 meter
Explanation:
First case 
Speed of car ( v )  = 20.5 mi/h  = 9.164  M/S
distance ( d ) = 11.6 meter                                       ( m = mass of the car )
Work done = 0.5 m v²  = 0.5 * 9.164² * m J  = 41.99 m J
Force = ( workdone /distance ) = ( 41.99 m / 11.6 )   =  3.619 m N
Second case 
v = 50.2 mi/h = 22.44135 m/s
d = ?
 Work done = 0.5 * 22.44² * m J = 251.7768 * m J 
Since the braking force remains the same .
3.619 m = ( 251.7768 m / d ) 
d = 69 .57 meter
 
        
             
        
        
        
The answer is B (The second one). I'm not sure though.
        
             
        
        
        
Answer:
1 atom of oxygen
2 atoms of hydrogen in each molecule
Each water molecule contains 3 atoms making the H2O formula
 
        
             
        
        
        
Answer:
Ionic compound. 
Explanation:
812° C is a very high melting point. Such high melting points are generally ionic compound. Ionic compounds are have very strong bond between the elements ( electrostatic bond). In order to break this bond, large amount of heat energies are needed. So, they have high melting point. Also, Ionic compound are very good conductors of electricity.
 
        
             
        
        
        
Surface currents are caused by winds. They move warm water away from the equator and cool water away from the poles. 
Hope it help