Answer to Question #221109 in Mechanics | Relativity for haro

Question

A boy pulls a wooden box along a rough horizontal floor at constant speed by means of a force P. In the diagram f is the magnitude of the force of friction, N is the magnitude of the normal force, and Fg is the magnitude of the force of gravity. Express the relationship of these forces?

Answer 1

Forces at the horizontal direction cancel, therefore$:Pcos\Theta-f = 0$ where, $P>F ; (0<\Theta>90°)$

Forces in the vertical direction also cancel therefore:

$$N + Psin\Theta-{f_g} = 0$$

Where $N = {f_g}-PsinΘ< {f_g}$

For each equation, we base on the fact that constant speed in one direction is zero acceleration

Therefore, $P>f$

$N<{f_g}$