To find the net force of the system, we will consider the forces acting in one direction as positive and those in the opposite direction as negative.
The cue ball is moving to the left with a force of 70 N, which we can assign as positive: \[ F_{\text{left}} = +70 , \text{N} \]
The four ball is moving to the right with a force of 50 N, which we will assign a negative value: \[ F_{\text{right}} = -50 , \text{N} \]
To find the net force, we add these two forces together: \[ F_{\text{net}} = F_{\text{left}} + F_{\text{right}} = 70 , \text{N} + (-50 , \text{N}) \] \[ F_{\text{net}} = 70 , \text{N} - 50 , \text{N} = 20 , \text{N} \]
Thus, the net force of the system is 20 N.
The correct response is: 20 N