Answer:
option D
Explanation:
given,
length of the pipe, L = 0.96 m
Speed of sound,v = 345 m/s
Resonating frequency when both the end is open
 
n is the Harmonic number
2nd overtone = 3rd harmonic 
so, here n = 3
now,
 
 f = 540 Hz
The common resonant frequency of the string and the pipe is closest to 540 Hz.
the correct answer is option D
 
        
             
        
        
        
I think to an observer outside the train, the speed of the ball will actually look like more than the speed of the train. 
        
             
        
        
        
Your answer is C) <span> the potential energy of an object is always greater than its kinetic energy </span>