Which diagram represents an object at static equilibrium?

A

Explanation:

As per the diagram four forces are applied on the box from four different direction.

In first case: F 1 = force exerted by ground in upward direction = 50 N

                    F2 = force due to gravity in downward direction = 50 N

In second case :  F3 = force exerted by player towards right side= 20 N

                            F4 = force due to friction towards left side = 20 N

so if we look at the forces, paired forces are equal and opposite hence they cancel out each other resulting the object to be in same position which means the object is in equilibrium state.

3. dark matter

empty space could also be a simple vacuum