Question

Two people are holding up the ends of a 4.25-kg wooden plank. A 6.00-kg box sits in the center of the plank. What forces do the people exert on the plank? Hint: The forces of the people must equal the forces acting on the box and the plank.

Answer 1

The forces the people exert on the plank is 100.45N

Explanation:

Force of man 1 on plank = $F_1$

Force of man 2 on plank = $F_2$

$\bold{\text{ \bold{ Acceleration due to gravity}} = 9.8 m/s^2}$

Gravitational force on plank = $\bold{m\times a = 4.25\times 9.8 = 41.65N}$

Gravitational force on box = $\bold{m\times a= 6\times 9.8 = 58.8N}$

Given hint is forces of people is equal to forces on plank and box

$\bold{\Rightarrow F-1 + F_2 = 41.65 + 58.8 = 100.45N}$

in the state of equilibrium normal force is equal and opposite to gravitational force.