1. Explain how you calculate the net force in any direction on the box. 2. Suppose an upward force of 15 N is added to the box. What will be the net vertical force on the box?
3. What force could be applied to the box to make the net force in the horizontal direction zero? Explain.
4. Suppose a force of 25 N to the right is added to the box. What will be the net force to the right?

1.Explain how you calculate the net force in any direction on the box.

If the two horizantal (left to right) forces act on an object in opposite directions and they don't exactly cancel out, what is left over is the net force In the diagram, the net force is 50 Newtons.

The equation you have to do (100 N - 50 N = 50 N).

If the two vertical (up and down) forces act on an object in opposite directions and they do cancel out, what is left over is the net force In the diagram, the net force is 0 Newtons. The equation you have to do. (25 N - 25 N = 0 N)

Final 50 N

2.Suppose an upward force of 15 N is added to the box. What will be the net vertical force on the box?

The net vertical force ( up and down) would be 15 N  

3.What force could be applied to the box to make the net force in the horizontal direction zero? Explain.

You could apply another horizontal (left to right) force of 50 N then the horizontal net force would be 0 N

4.Suppose a force of 25 N to the right is added to the box. What will be the net force to the right?

If suppose I say I added a horizontal (left to right) net force of 25 right next to the 50 N. The net force for the whole box would be 25 N.