Final answer:
The box in the bus aisle moving backward can be explained by Newton's First Law of motion, frictional force, or uneven distribution of forces within the bus.
Step-by-step explanation:
If a box at rest in the aisle of a bus suddenly starts to move backward, it can be explained by Newton's First Law of motion, also known as the law of inertia. According to this law, an object at rest will remain at rest unless acted upon by an external force. In this case, the box starts moving backward because the bus accelerates forward, pushing the box in the opposite direction.
Another possible explanation could be a frictional force acting on the box. If the bus suddenly decelerates, the box can slide backward due to the inertia of its own mass. The friction between the box and the floor of the aisle can cause it to move.
Finally, the movement of the box can also be explained by the uneven distribution of forces inside the bus. For example, if there is a sudden change in the weight distribution or a strong vibration, the box can be subjected to a net force that causes it to move backward.
Learn more about Newton's First Law of motion