A) you push against a box; it doesn't move. is the net force of the box in this situation balanced and at zero? or is it unbalanced?

F = M A. Ican't type that big enough ! ==> If the net force on the box is not zero, it would be accelerating.

==> If the box is not accelerating, the net force on it must be zero.
If there ARE any forces acting on it, they must be balanced, since they add up to zero.

Jet streams are relatively narrow bands of strong wind in the upper levels of the atmosphere. the winds blow from west to east in jet streams but the flow often shifts to the north and south. jet streams follow the boundaries between hot and cold air. the earth's rotation is responsible for the jet stream as well.