explain why some of the leaves may get detached from a tree if we vigorously shake its branch

Some leaves may get detached from a tree if its branch is vigorously shaken due to the force of inertia. When the branch is shaken, it moves rapidly, but the leaves tend to remain at rest because of their inertia, which resists sudden changes in motion. This causes a mechanical stress on the connection between the leaves and the branch. Additionally, leaves are connected by small stems (petioles) that can only withstand a certain amount of force. Vigorous shaking applies enough force to break or weaken the attachment, especially at the abscission layer, a specialized layer of cells where leaves naturally detach. As a result, some leaves get detached and fall off.