1)discuss whether an object can be moving if the net force acting on th object is zero.
2)for the following actions, explain whether the forces involved are balanced or unbalanced
a)you push a box until it moves.
b)you push a box but it doesn't move.
c)you stop pushing a box and it slows down.

1). Contrary to what we think we see around us every day, NO force is required
to keep an object moving at a constant speed in a straight line. 

Force is required to change the object's motion . . . speed it up, slow it down,
or change the direction in which it's moving.

2.a). The motion of the box changes from not moving to moving. 
The forces on it are unbalanced.

2.b). The motion of the box doesn't change. It goes from not moving to
still not moving. The forces on it are balanced.

2.c). The motion of the box changes from moving to moving slower. 
After you stop pushing, the forces on it are unbalanced.