Answer:
a - As long as the time between 2 events is reconcilable with a light signal, the time between the events, in that frame, can be determined.
 
        
                    
             
        
        
        
On an approximate scale, A child breaths 20 times a minute as compared to only 12 to 16 in resting phase of an Adult.
So, In 60 minutes (1 hour), They breathe = 20 * 60 = 1200
In 24 hours (1 day), They breathe = 1200 * 24 = 28,800
In short, Your Answer would be: 28,800
Hope this helps!
        
                    
             
        
        
        
Acceleration = force / mass.
A = 100/50 = 2 m/s^2 .
        
             
        
        
        
The difference in electric potential energy between the two points is

where q is the magnitude of the charge and 

 is the electric potential difference.
But for energy conservation, the difference in electric potential energy 

 between the two points is equal to the work done to move the charge between A and B:

so we have

and by substituting the numbers of the problem, we find the value of 

:
 
 
        
        
        
Answer:
Yes , it is possible  for two different atoms of carbon to have different numbers of neutrons in their nuclei .
Explanation:
Isotopes -
Atoms of the element with same number of the electrons and protons , but differ in the number of neutrons , are called as the isotopes .
The isotopes of the element have the same number of protons and electrons , hence have the same chemical and physical properties .
Many isotopes occurs naturally .
In case of Carbon ,  
Carbon too have isotopes ,  
i.e.  
Carbon - 13 and Carbon - 14
carbon - 13 , have seven neutrons  
Carbon - 14 , have eight neutrons .