Question

A person (40 kg) is managing to be at rest between two vertical walls by pressing one wall A by his hands and feet and the other wall B by his back (figure 6−E11). Assume that the friction coefficient between his body and the walls is 0.8 and that limiting friction acts at all the contacts. (a) Show that the person pushes the two wall with equal force. (b) Find the normal force exerted by either wall on the person. Take g = 10 m/s².

Figure

Answer 1

Thus, we have:
μR + μR = mg
⇒ 2μR = 40 × 10
$\Rightarrow R=\frac{40\times 10}{2\times 0.8}=250\mathrm{N}$
Normal force = 250 N