A heavy ball is suspended as shown in the figure given below. A quick jerk on the lower string will break that string but a slow pull on the lower string will break the upper string. The first result occurs because Lower string

The experiment demonstrates the concept of inertia, which is the inherent property of a body to resist changes in its state of motion. When a quick jerk is applied to the lower string, the force is transmitted rapidly. However, the heavy ball possesses significant inertia, which prevents it from accelerating or moving downward quickly enough to stretch and break the upper string [t3][t4]. Consequently, the tension in the lower string increases abruptly beyond its breaking point before the ball can move appreciably [t4][t7]. In contrast, a slow pull allows the force to be transmitted through the ball to the upper string. In the slow case, the upper string supports both the applied force and the weight of the ball (mg), causing it to reach its breaking threshold first [t4][t6]. Thus, the first result occurs specifically because the ball has inertia [t3].