When an apple is on a tree, the force acting on it is balanced. The force of gravity pulling the apple down is balanced by the force of the stem holding the apple up. This means that the net force on the apple is zero, and it remains stationary.

If the stem were to break, the force of gravity would no longer be balanced, and the apple would fall to the ground. This is because there would be no force acting upwards to counteract the force of gravity.