Question

Tony, a yoga instructor is holding a plank. He has a weight of 585 N and the distance from his center of gravity to his feet is L1 = 0.841 m, while the distance from his center of gravity to his hands is L2 = 0.416 m. What is the normal force exerted by the floor on both of his hands? O 108 N O 392 N 445 N O 357 N 279 N

Answer 1

Weight of Tony w = 585 N;

Let the normal reaction force by floor to feet and both hands is $R_1$ and $R_2$ respectively.

Take moment about the feet of the instructor;

$+wL_1-R_2(L_1+L_2)=0$

$wL_1=R_2(L_1+L_2)$

$585 \times 0.841 = R_2 (0.841 + 0.416)$

$R_2=391.396\approx 392\ N$ (normal force on both hands)