Answer:
The normal force arrow should have same length of the gravity arrow, but opposite direction (so, upward)
Explanation:
The box is motionless: this means that its velocity is zero, and also that its acceleration is zero.
Zero acceleration means that the net force on the box is also zero, according to Newton's second law:
[tex]F=ma=0[/tex]
This means that the two forces acting on the box (gravity and normal force) must balance each other to produce a zero net force: therefore, the two forces must have same magnitude (so, the two arrows must have same length), but opposite direction (and since gravity acts downward, the normal force must be upward).
