Inertia - Which String Breaks

A heavy mass suspended by a top string has a string hanging from the bottom. A quick pull on the lower string causes it to snap due to the ball’s inertia, while a slow pull causes the top string to break because it the gravity of the mass add to the force.

1. Suspend a heavy mass from a sturdy support using a strong top string.
2. Attach a string to the bottom of the ball so it hangs freely.
3. Pull the lower strings very quickly with a sharp tug. Observe that the bottom string snaps because the ball’s inertia resists sudden motion.
4. Retie and pull the bottom string very slowly and steadily. Observe that the top string breaks because it experiences greater tension than the bottom string in this case.
5. Discuss the difference between the outcomes of quick versus slow pulls in terms of inertia and tension forces.

Inertia explained by breaking a string - PhyicsIsFun:

Inertia Demonstration. Which String Breaks? - PrerequisiteName:

📄 Inertia Ball Breaks String - UChicago Instructional Physics Laboratories: https://www.physlab-wiki.com/physicsdemos/mechanics/newtons_laws/inertia_ball_breaks_string

• Use weights of different masses to see how mass affects which string breaks.
• Attach a spring scale to measure the force applied during slow pulls.

• Ensure the weight is not too heavy for the support or strings, to avoid falling hazards.
• Use strong supports to prevent accidental collapse.
• Keep faces and hands clear of the path of snapping strings.

• Why does the bottom string break during a quick tug but the top string break during a slow pull?
• How does inertia explain the outcome of the quick pull?
• Why is the tension greater in the top string during a slow pull?
• How does the mass of the ball affect the results?
• Can you think of everyday examples where pulling quickly versus slowly makes a difference (e.g., pulling off a bandage, snapping a tablecloth)?