Question

question 3 of 10
a man with mass 81 kg lies on the floor. what is the normal force on the man?
a. 794 n
b. 713 n
c. 820 n
d. 855 n

Explanation:

Step1: Identify the forces acting on the man

The man is at rest on the floor. The forces acting on him are the gravitational force ($F_g$) pulling him downwards and the normal force ($F_N$) pushing him upwards. According to Newton's first - law, since the man is in equilibrium ($a = 0$), the net force in the vertical direction is zero, i.e., $F_{net,y}=F_N - F_g=0$, so $F_N = F_g$.

Step2: Calculate the gravitational force

The formula for gravitational force is $F_g=mg$, where $m = 81$ kg and $g = 9.8$ m/s². So $F_g=81\times9.8=793.8$ N. Since $F_N = F_g$, $F_N\approx794$ N.

Answer:

A. 794 N