A. Positive acceleration represents an object speeding up; negative acceleration represents an object slowing down.
B. Positive acceleration moves north or east; negative acceleration moves south or west.
C. Positive acceleration occurs when there is more velocity than speed; negative acceleration occurs when there is less velocity than speed.
D. Positive acceleration occurs when an object changes its speed but not its direction; negative acceleration occurs when an object changes both its speed and direction.
Well it has nothing to do with speeding up or slowing down. Positive acceleration is just gaining speed IN THE DIRECTION that you decided to call the positive direction when you started working on the problem.
Example:. If UP is the posititive direction, then the acceleration of gravity is negative. An object in free motion will have unbalanced downward force on it ... negative force ... and it will gain speed downward, and that will be a negative acceleration. It's just how you set up the problem. You called UP the positive direction. That's fine. It's completely up to you.
