Question

A brick is lying on a table in a state of static equilibrium. If the mass of the brick is 7.52 kilograms, what is the normal force exerted by the table on the brick?
A. −73.7 newtons
B. 73.7 newtons
C. 80.7 newtons
D. 7.52 newtons
E. 8.07 newtons

I believe the answer is either A. or B.—I'm just not sure if it should be expressed as a negative or not because the force is acting in the opposite direction. 

Answer 1

In mechanics, the normal force is the component, perpendicular to the surface (surface being a plane) of contact, of the contact force exerted on an object . We calculate as follows:

∑F along x = 0 = F - Fn

Fn = F = mg = 7.52(9.81) = 73.77 N <------OPTION B