Astudent along with her backpack on the floor next to her, are in an upward-moving elevator that is coming to a stop with an acceleration that decreases linearly in time from an initial value of a. the student gives her backpack a quick kick causing it to slide across the elevator, which has a coefficient of friction μ between itself and the backpack. what is the minimum speed that the student needs to impart to the backpack for it to hit the wall of the elevator, a distance d away by the time the elevator stops?