(Solved): Two students are discussing the importance of the direction of the acceleration vector for two obje ...

Two students are discussing the importance of the direction of the acceleration vector for two objects moving in 1-Dimension. They agree that it has something to do with whether the object speeds up or slows down, but beyond that they're confused. Which of the following best explains the how the acceleration vector's direction relates to whether an object speeds up or slows down? When the acceleration vector points parallel to the object's present non-zero velocity the object speeds up. If the acceleration points anti-parallel to the object's present (non-zero) velocity it slows down. If the object is presently at rest it speeds up no matter the direction of the acceleration vector. None of the others is true. Whether the object speeds up or slows down depends on which direction we call positive and what direction we call negative. If the acceleration vector points in the positive direction the object slows down and if the acceleration vector points in the negative direction the object speeds up. If the acceleration vector points in the positive direction the object speeds up and if the acceleration vector points in the negative direction the object slows down.