1) The following is the list of forces acting on the cup:
- the weight of the cup (mg), acting downward
- the normal reaction of the table (N), acting upward, that balances the weight of the cup
- the horizontal force of 0.7 N that pushes the cup
- the frictional force ([tex]\mu N[/tex]), acting horizontally but in the opposite direction of the previous force, that prevents the cup from sliding
2) The net force acting on the cup is 0 N. In fact, the cup is at rest, so its acceleration is zero: for Newton's second law, if an object is not accelerating, it means the net force acting on it is zero:
[tex]\sum F = ma[/tex]
where the term on the left is the resultant of the forces acting on the object, m is its mass and a its acceleration. Since the acceleration a is zero, the term on the left must be zero as well.
