Ultraviolet (UV) light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, that is, in the range 10 nm to <span>400 nm</span>
        
             
        
        
        
Answer:
b. 375 N
Explanation:
System of forces in balance
ΣFy = 0 Equation (1)
Forces acting on the board
T₁: Tension in the  left chain ,  vertical and upward
T₂ = 250 N : Tension in the right chain ,  vertical and upward
W₁ = 125 N : Weight of the  board , vertical and downward
W₂ =  500 N : Weight of the  person , vertical and downward
Calculation of the T₁
We apply the Equation (1)
ΣFy = 0  
T₁+T₂-W₁-W₂ = 0
T₁ = -T₂+W₁+W₂ 
T₁ = -250 N+ 125 N+ 500 N
T₁ = 375 N
 
        
             
        
        
        
Green would be best 
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The ball can't reach the speed of 20 m/s in two seconds, unless you THROW it down from the window with a little bit of initial speed. If you just drop it, then the highest speed it can have after two seconds is 19.6 m/s .
If an object starts from rest and its speed after 2 seconds is 20 m/s, then its acceleration is 20/2 = 10 m/s^2 .
(Gravity on Earth is only 9.8 m/s^2.)
        
             
        
        
        
The hypothesis because its very hard to make and it confounds me