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
The gravitational force between two masses is given by:

where
G is the gravitational constant
m1 and m2 are the two masses
r is the separation between the two masses
We see that the force is proportional to the inverse of the square of the distance:

therefore, if the distance is tripled:
r'=3r
The force decreases by a factor 1/9:

Since the original force was 36 N, the new force will be
Amplitude is the pair of vertical buttons, so to speak. Compressions are the bunched up vertical lines with the purple arrows pointing left and right. Rarefactions are purple arrows pointing down. Wavelength is crest to crest purple buttons. Associated LH and RH pointing arrows.
After 5 seconds the stone will have fallen 49 m