In your own words, explain why laws cannot become theories. include one example to support your response.

 Laws are mathematical relationships that describe an observed phenomena e that are consistently found to be true.Theories scientifically explain how or why the natural phenomena occur.  
Theories cannot become laws because each serves a different purpose.
Newton's theory of gravity explained that there was an attraction between mass similar to the attraction due to electron static forces.It turns out Newton's theory was  incomplete, but Newton's Law of Gravity remains true at least at normal speeds and masses found in the universe

The first thing you have to do for these problems is to define the appropriate control volume.
 When you have the control volume, the next thing is to correctly write the Energy equation between two points.
 Finally, you should use the continuity equation if required.
 I attached the solution.