Give the direction of the net force acting on each of the following objects. If the net force is zero, state "zero."
(a) A car accelerating northward from a stoplight.
(b) A car traveling southward and slowing down.
(c) A car traveling westward with constant speed.
(d) A skydiver parachuting downward with constant speed.
(e) A baseball during its flight from pitcher to catcher (ignoring air resistance).