Answer:
 v = 9.936 m/s
Explanation:
given,
height of cliff = 40 m
speed of sound = 343 m/s
assuming that time to reach the sound to the player = 3 s
now,
time taken to fall of ball 


t = 2.857 s
distance 
d = v  x t
d = v x 2.875 
time traveled by the sound before reaching the player



distance traveled by the wave in this time'
r = 0.143 x 343
r= 49.05 m
now,
we know.
d² + h² = r²
d² + 40² = 49.05²
d =28.387 m
v x 2.875=28.387 m
 v = 9.936 m/s
 
        
             
        
        
        
Answer: Current needed, mA 20 Voltage needed, V AC 6
Explanation: An electric gradient (or field) can exist that is analogous to the situation described above for step and touch potentials. The situation is more complex to analyze in the water because a person in the water assumes different postures and orientations in 3 dimensions (up, down, and sideways—north, south, east, and west). The transthoracic and translimb voltages will vary as the person moves in relation to the orientation (direction) of the electric field.
 
        
             
        
        
        
I believe the answer is convection! 
        
             
        
        
        
Nuclear energy has practically no harmful emission (unless you consider water vapour to be bad).