Answer:
If you count the number of seconds between the flash of lightning and the sound of thunder, and then divide by 5, you'll get the distance in miles to the lightning: 5 seconds = 1 mile, 15 seconds = 3 miles, 0 seconds = very close. Keep in mind that you should be in a safe place while counting.
Explanation:
 
        
             
        
        
        
Answer:closed systems
Explanation:
A closed system is one in which matter does not enter or leave the system but there is exchange of energy between the system and its environment. In a closed system, the principle of energy conservation applies. The principle of energy conservation states that energy can neither be created nor destroyed but is converted from one form to another. An example of a closed system is a reaction vessel whose lid is closed.
 
        
                    
             
        
        
        
The wavelength of the note is 

. Since the speed of the wave is the speed of sound, 

, the frequency of the note is

Then, we know that the frequency of a vibrating string is related to the tension T of the string and its length L by

where 

 is the linear mass density of our string.
Using the value of the tension, T=160 N, and the frequency we just found, we can calculate the length of the string, L:
 
 
        
        
        
A group of protons and neutrons surrounded by electrons 
 
        
             
        
        
        
Answer:
i think the answer is constant