Answer: Option (b) is the correct answer.
Explanation:
The given data is as follows.
          F =  N
 N
          g = 9.8 m/s 
          radius =  
 
                     =  = 15 cm = 0.15 m   (as 1 m = 100 cm)
 = 15 cm = 0.15 m   (as 1 m = 100 cm)
Formula to calculate depth is as follows.
         F = 
or,      h =  
        
        h =  
 
            = 751 m
Thus, we can conclude that the maximum depth in a lake to which the submarine can go without damaging the window is closest 750 m.
 
        
             
        
        
        
The density of the material would be 
25/6 grams per cm^3.
to obtain the result above this is what we do:
density is calculated as: (the mass of the given material or object) / volume of the material 
which leads us to 50grams /12cm^3
 
        
             
        
        
        
A. 0.5kg
To get this answer you need to follow the equation of KE=0.5*mv^2 
But we don't have the m part in the equation. So just plug in the numbers to see which works best, though I can tell you before we do that the answer would be a. 
As you may know, gravity, is a force of 9.8 m/s. And we want to get 9.8 Joules. So if we take a half a kg stone, release it at one meter, we get half of the normal gravity pull, 4.90 Joules. That means if we take half a kg stone and drop it at a doubled height, we get 9.8 Joules.
That is also to say that if we have a 1kg stone and drop it at one meter you will get the normal pull of gravity in Joules, 9.8J. 
Be careful though, this does not mean if you drop a 1kg stone and a .5 kg stone the 1kg will hit first. This simply means that the 1kg stone will have twice the Joules that the .5kg stone has.
        
                    
             
        
        
        
The right answer to this question is A. a crest that is toppling over. When a surfer rides an ocean wave on her surfboard, she is actually riding on a crest. The crest is the point on a wave with the maximum value or upward displacement within a cycle.