Standards Alignment (xls)
- Clearing up Cola (5, 8)
- Hot Chocolate Effect (6, 8)
- Upside Down Water (3)
- Inertia Beads (3)
- Gauss Gun (4)
- Air Cannon (3)
- Cartesian Diver (6)
- Pocket Sling Shot(K, 1, 3, 5, 7)
- Screaming Balloon (2, 6)
- Easy Soap Slime (4, 5, 8)
- Mind Control Motion (1, 4)
- Refrigerator Magnet Poles (1, 4, 7)
- Hanger Gong (2, 6)
Upside Down Glass of Water Part 2
What if you turn your glass upside down and take off the index card? Will the water still stay in the glass? With a little help from science it can!
Mason jar with ring
Cheesecloth (wire mesh or screen will work as well)
Cut out a piece of cheesecloth a bit larger than the top of the mason jar. Lay the cheesecloth on top of the jar and screw the ring on top to hold the cheesecloth in place. Pour water into the jar until it is at least half full. . Hold the jar with one hand and put your other hand flat over the index card. Quickly flip the jar upside down. Remove your hand from the index card. Slowly slide the index card off the glass. Does the water stay in the jar? Tap your finger against the cheesecloth. Does the water still stay in the jar?
Without the index card in place, surface tension is the main force holding the water in the jar. If you look carefully at the cheesecloth while the jar is upside down you can see the water bulging slightly through each hole. The water molecules stick to each other forming a surface tension skin on the surface of the water. This sticky surface tension keeps the water from leaking through the holes.
What if you used a mesh with larger holes? How big can the holes be so that surface tension keeps the water in the jar? How much or little water is needed for the water to stay in the jar?
Carl Friedrich Gauss was a German mathematician who did much of his work in the early 1800’s. He is known not just for his mathematical discoveries but also for his work with electromagnetism. In fact the unit of magnetism is named after him – the Gauss! A Gauss gun uses magnets to accelerate a projectile.
2 or more neodymium magnets
3 or more steel ball bearings (about the same size as the magnets)
Ruler with a groove in the middle or two dowels glued together
Strong tape (packing or duct tape works well)
*Keep neodymium magnets away from small children who might swallow them. Also keep the magnets away from cell phones and other electronic devices. These strong magnets can cause permanent damage.
Place two ball bearings right at the end of the ruler and then one magnet next to the balls. Tape the magnet securely in place. Slide the ruler so the ball bearings and magnet are right at the edge of the table. Trim off any extra tape on the sides of the magnet.
Make sure no one is in the way and gently roll another ball bearing along the ruler towards the magnet. The ball bearing on the end will shoot out and land on the floor!
Roll the ball at different speeds and from different distances. How does this change the speed, and therefore the distance traveled by the last ball bearing?
When the ball rolls towards the magnet it accelerates, or speeds up, because the magnet is pulling on it. As it speeds up it gains kinetic, energy, the energy of motion. When the first ball hits the magnet, that energy is transferred to the magnet and the balls on the other side. The ball at the end shoots off with almost the same kinetic energy that the first ball had when it hit the magnet. Some of the energy is lost to sound and heat but most is transferred to the ball at the end. If you add another stage – another set of magnets and balls – after the first magnet you can accelerate the ball even faster so it travels even further from the table. Try it!
What if you have more than two ball bearings behind the magnet, or just one? What if you use different size ball bearings or magnets? How does this affect the distance traveled by the last ball?
What if you set up a two or three stage Gauss gun? Tape another magnet a couple of inches behind the first and place two more ball bearings right behind it. Roll the ball to the first magnet, which shoots another ball into the second magnet, which shoots the last ball. How does this affect the distance traveled by the last ball? How many stages can you add to the gun?
What if you measure the exact distance traveled by the ball bearings? Tape carbon paper on top of white paper onto the floor. The balls will leave a mark where they land. Or use a large container or baking pan filled with sand to catch the balls.
Basic Air Cannon
Use a simple cardboard box to shoot air all the way across the room!
Large Box (at least 12 inches long and 12 inches wide)
If your box has any loose flaps, tape them in place so you have a sealed box. Use the scissors to cut a hole about 4 inches across on a small end of the box.
Stack a pyramid of Styrofoam cups as a target for your vortex cannon.
Stand about 3 feet away from the cup pyramid. Aim the open end of the cannon at the cups. To shoot the cannon take both hands and slam them on the sides of the box. An air cannonball will knock over the cups! Keep moving back to see how far away you can use the vortex cannon to knock over the cups.
What if you use a different size box or a different size hole? Does this affect how far your air cannon can shoot?
When you shoot an air cannon, the air inside gets pushed out through the hole. As this air comes out of the hole it pushes the air that was already there out of the way, creating a twisting doughnut of air called a toroidal vortex. A vortex describes the twisting and swirling of a fluid. You have probably seen a vortex when you drain the bathtub or watch water swirl around rocks in a stream. Vortices are special because the motion is stable and doesn’t need any help to keep its shape. The toroidal vortex from your air cannon is so stable it will travel all the way across the room before it falls apart. If you add smoke to your cannon you can see exactly how far it goes!
Send a ketchup packet on a deep sea adventure!
Empty 2-liter bottle
Ketchup packets (or whatever other condiment packets you have handy)
Fill the tall glass most of the way full of water. Put the ketchup packets into the glass one at a time and observe if they float. Find a packet that floats at the top of the glass but just under the water level. Keep this packet and put away the rest.
Remove the label from the 2-liter bottle and fill it with water. Put the ketchup packet in the bottle, fill it all the way to the top with water and put the cap on tightly.
Place both hands on the bottle and squeeze. What happens to the ketchup packet in the bottle?
The ketchup packet floats because it has a small amount of air inside. When you squeeze the bottle you also squeeze the ketchup packet and compress the air just enough so that it becomes more dense and sinks. When you let go of the bottle the air expands again and the ketchup diver returns to the top.
What happens if you use the ketchup packets that float on top of the water? Or those who floated lower in the glass?