In a recent video, we explored five fascinating physics phenomena that might seem mysterious at first. Many people shared their thoughts and questions, and now we’re diving into the explanations behind these cool occurrences. Let’s start with the surprising behavior of cereal in a magnetic field.
Did you know that cereal can be magnetic? By grinding cereal into a fine powder and using strong magnets, we can see it stick to the magnets. This happens because cereal contains added iron, which is an important nutrient. Iron is magnetic, and it makes up about 60% of the recommended daily intake of iron.
But there’s more to the story! A viewer named Martin Bear noticed that non-magnetic things like plastic and paper seemed to be attracted to the magnet too. This is because of water’s special property called diamagnetism. When water is near a magnet, it creates a magnetic field in the opposite direction, causing a slight repulsion. This makes a small dip in the water’s surface. When floating objects like cereal are placed on this surface, they slide into the dip, making it look like they’re attracted to the magnet.
Next, we learned how to find the center of mass of a stick-like object, like a cane. You can do this by moving your fingers toward the center from the ends. One finger will feel more weight and have more friction, causing it to slow down until the other finger catches up. Eventually, both fingers meet at the center of mass.
Have you ever tried flipping a phone end over end? It’s tricky because the phone has three axes of rotation: the long axis, the short axis, and the intermediate axis. The intermediate axis theorem tells us that if you flip an object along its intermediate axis, it won’t stay in that rotation and will also rotate around the other axes. This is like trying to balance a pendulum on its end—any small movement can cause big changes in motion.
Another cool experiment showed how an electrically charged object can deflect a stream of water. You might think this happens because water is polar, but the real reason is the dissolved ions in the water. When a negatively charged cup is near the water stream, it repels negative ions, making the water slightly positively charged. As the water breaks into droplets, these positively charged droplets are attracted to the negatively charged cup, causing the water to bend.
Finally, we looked at the teabag rocket experiment. When a burning teabag takes off into the air, it’s because the air inside the teabag heats up, expands, and becomes less dense than the cooler air around it. The cooler air pushes the lighter, heated air upward, creating a buoyant force. When the teabag burns down to ash, the lightweight ash is carried up by the convection current, making it look like a rocket!
These explanations reveal the amazing physics behind everyday phenomena. What do you think about these interpretations? Were you able to figure out these puzzles on your own? Share your thoughts, and thanks for exploring these fun physics concepts with us!
Gather some cereal and a strong magnet. Grind the cereal into a fine powder and see if you can get it to stick to the magnet. Discuss with your classmates why the cereal is magnetic and how iron plays a role in this phenomenon. Can you think of other foods that might have similar properties?
Find a stick-like object, such as a ruler or a cane. Try to find its center of mass by moving your fingers from the ends toward the center. Notice how one finger slows down due to friction. Discuss why this happens and how it relates to the center of mass. Can you find the center of mass of other objects in the classroom?
In pairs, try flipping a phone or a similar object along its intermediate axis. Observe how the object behaves and discuss why it doesn’t stay in that rotation. Relate your observations to the intermediate axis theorem. Can you think of other objects that might behave similarly?
Use a plastic comb or a balloon to charge it by rubbing it on your hair or a wool sweater. Hold it near a thin stream of water from a faucet and observe how the water bends. Discuss why this happens and the role of dissolved ions in the water. Try using different charged objects and see if the effect changes.
Carefully cut open a teabag and empty its contents. Form the teabag into a cylinder and place it on a non-flammable surface. Light the top of the teabag and watch as it takes off. Discuss the physics behind this experiment, focusing on convection currents and buoyancy. What other materials might create a similar effect?
Cereal – A type of grain used in scientific experiments to demonstrate properties like density and buoyancy. – In the lab, we used cereal to observe how different materials float or sink in water.
Magnetic – Having the property of attracting certain metals, like iron, due to a magnetic field. – The magnetic force of the magnet was strong enough to lift small iron filings.
Iron – A metal that is attracted to magnets and is often used in experiments to study magnetism. – We placed a piece of iron near the magnet to see how quickly it would be attracted.
Water – A liquid that is essential for life and is used in many scientific experiments to study properties like density and buoyancy. – When we added salt to the water, we observed how it affected the buoyancy of the egg.
Mass – The amount of matter in an object, usually measured in grams or kilograms. – We used a balance to measure the mass of the rock, which was 250 grams.
Axis – An imaginary line around which an object rotates. – The Earth rotates around its axis, which is why we have day and night.
Charged – Having an electric charge, which can be positive or negative. – The balloon became charged when we rubbed it on the wool sweater, allowing it to stick to the wall.
Stream – A flow of liquid or gas, often used to describe the movement of particles in physics. – We observed the stream of water as it flowed through the narrow pipe in our experiment.
Rocket – A vehicle or device propelled by the expulsion of gases, used to study principles of motion and force. – The model rocket soared into the sky, demonstrating Newton’s third law of motion.
Force – A push or pull on an object that can cause it to change its velocity. – We calculated the force needed to move the box using the equation $F = ma$, where $m$ is mass and $a$ is acceleration.
