This demonstration shows how inertia works by striking a knife that has been inserted into a potato. The potato resists sudden motion, so the knife moves deeper into it, illustrating Newton’s First Law of Motion.

1. Take a raw potato and place it securely on a stable surface.
2. Insert the tip of a knife (or sturdy skewer) a short distance into the potato.
3. Hold the potato steady or have it supported so it does not roll.
4. Using a hammer or another hard object, give the handle end of the knife a sharp strike.
5. Observe how the knife drives deeper into the potato. It may appear that the potato moves upward, but in reality, the potato’s inertia resists motion and the knife moves instead.

Will It Drop? Potato Physics With a Knife! - TAMU Physics & Astronomy:

📄 Inertia Demo (3/4 down the page) - Weebly: https://apphysicsisps.weebly.com/ap1-unit-2-labs.html

• Try the experiment with an apple.
• Vary the strength of the strike to see how inertia affects the depth of penetration.

• Exercise caution when using knives, hammers, or sharp tools—adult supervision required.

• Why does the potato appear to move upward when the knife is struck?
• How does inertia explain why the potato resists sudden changes in motion?
• What would happen if you pushed the knife slowly instead of striking it?
• Can you think of other real-life situations where inertia explains the motion of objects (e.g., tightening a hammer head, passengers lurching forward in a car)?