Question

part 9 - mechanical comprehension
which of the following is the main force that acts on a
box sitting on a shelf?
a gravity
b torsion
c friction
d tension
click the button or type the letter next to your answer.

Explanation:

To determine the main force on a box on a shelf, we analyze each option:

• Option A (gravity): Gravity is the force pulling the box downward toward Earth’s center. For an object at rest on a shelf, gravity acts vertically downward.
• Option B (torsion): Torsion is a twisting force, irrelevant here as the box is stationary and not twisted.
• Option C (friction): Friction opposes motion; since the box is not moving, friction is not a main force (it would act only if the box tried to slide).
• Option D (tension): Tension is a pulling force (e.g., in ropes), not applicable to a stationary box on a shelf.

Gravity is the primary force acting downward, balanced by the shelf’s normal force upward.

Answer:

A. gravity