Jenny is traveling southward. In order to stop, she needs a northward acceleration.
A better way to say it:
Jenny is traveling southward in her bumper car, so the direction of her velocity is south. In order to reduce her velocity to zero, a velocity of equal magnitude but directed north must be added to it. Then the change in velocity is positive northward, and the change in velocity per unit time is acceleration.
What is this on, is this on a test?
Choice 'b' is one possible way to state
Newton's second law of motion.
The other choices are meaningless.
