BIZARRE spinning toys | Summary and Q&A

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May 4, 2016
by
Physics Girl
BIZARRE spinning toys

TL;DR

Spinning tops and eggs defy gravity and exhibit complex rotational physics due to changes in kinetic and potential energy, angular momentum, and torque.

Key Insights

• 😥 Spinning tops and eggs exhibit complex rotational physics, which fascinated physicists to the point of conducting extensive analyses.
• 📐 Changes in kinetic and potential energy, angular momentum, and torque are crucial in understanding the behavior of spinning objects.
• 🖐️ Friction plays a significant role in providing the torque needed for a spinning object to stand up against gravity.

Transcript

[MUSIC PLAYING] So I got this fancy top called a PhiTOP, which is just an oblong piece of metal. But watch what happens when you spin it lying down. It stands up. That is, if you start it spinning along its minor axis, it will rise up and spin along its major axis. Now, this toy is shiny and pretty, but that physics trick at the end, you could make... Read More

Q: Why does the center of mass of a spinning top or an egg rise when it stands up?

The rising center of mass is a result of converting kinetic energy into potential energy, due to changes in the object's rotational motion.

Q: What is the role of torque in making a spinning top or an egg stand up?

Torque, caused by applied forces and friction, changes the object's angular momentum, allowing it to stand up against gravity.

Q: Why do spinning tops and eggs behave differently on surfaces with little friction?

Without friction, there is no torque to oppose the motion, causing the objects to not stand up like they do on surfaces with friction.

Q: Why doesn't a raw egg stand up when spun?

The fluid inside the raw egg does not move with the shell, leading to a lack of torque and preventing it from standing up.

Summary & Key Takeaways

• When a spinning top or an egg stands up on its end, the center of mass rises, seemingly defying gravity.

• Energy conservation explains how this is possible, as kinetic energy is converted into potential energy.

• Torque, caused by friction and applied forces, changes the angular momentum of the spinning object, allowing it to stand up.