The object with a net force of -5 N down is the object with the force F_p acting downward with a magnitude of 5 N.
The free body diagram consists of four objects: The net force on an object is found by adding up all the individual forces acting on it.
In this case, we have three forces acting on the object: FN (normal force), Fg (gravitational force), and Fp (unknown force).
Since the net force is calculated by summing up the individual forces, we can find it by adding the magnitudes of the forces and considering their directions.
In this case, we have a net force of -5 N down, which means that the force Fp is acting downward with a magnitude of 5 N.
The probable question may be:
The free body diagram four object are shown line F_N and F_g intersect line F_f and F_p.
F_N=10 N
F_g=-10N
F_f=-15N
F_p =10N
Which object has a net force of -5 N down?