Tag: Physics

3D design with Tinkercad

Today our daughter designed this cat in tinkercad. It is a program you can use for free on their website. If you have a 3D printer you can print out your design. She had not tried that programme before, but designed it on her own. We have a friend who has a 3D printer visiting and he told her a few things to improve, and she then did that on her own.

This is what it looks like on the screen.

Our friend then sent the design to his 3D printer at home. He has a camera hooked up to the printer, so we could follow her design being printed on our phone.

Density, water + salt with an egg

Put an egg in water and observ that it does not float.

Put salt in the water and see the egg start to float on the water. Mix more water in, and see it sink again.

This is an easy experiment to do in the kitchen, but such a great part of how density works.

When we swim in the ocean we will find it easier to float or swim, than in freshwater. This is because the water density is higher in saltwater, than in freshwater.

If we would try to swim in oil, which has a lower density than freshwater and saltwater, we would find it very hard to stay above the surface.

We made a Corn Starch Monster

If you have some old speakers lying around, a good way to say goodbye to them, is making a Corn Starch Monster on them.

Maizena (corn flour) or Potato Starch works well. Mix it with water until it becomes a liquid base.

Then pour the mixture on the speaker and start it on a low frequency, around 20 Hz. The Starch will then start dancing.

The water and cornstarch mixture is a non-Newtonian fluid, and this means it behaves very oddly. You can pick it up, and if you keep moving it about so it’s under stress, it stays solid. But as soon as you let it rest, it goes back into a liquid.

Dry Ice Bomb in Plastic Bottle

We have really great friends. Some of them are that kind of friends that call you and say:”Hi, I just got hold of 20 kilo of dry ice, wan’t me to come by and make some experiments?”

“Sure we do! Let’s have fun and explode the childrens Swimming Pool at the same time!” We said.

The children learned about cold temperatures and the power of dry ice. It is just as dangerous as hot things.

What happens is that the dry ice melts and turns into CO₂ gas. The gas takes up more space than the ice did, and the pressure in the bottle increases. As the lid of the bottle isn’t strong enough to hold such hig pressure, it is shut of the bottle like a bullet.

 

Electrolysis of water and salt, 9v battery, 2 screws and an elastic

“Can you take a water molecule apart?” the children asked. “Yes you can, but you have to use Electrolysis”, my husbond said.

The talk came from talking about, how much Hydrogen there is in the universe. Actually 73% of the universe consists of Hydrogen and the children wondered why it doesn’t explode.

They also wondered why water puts out fire, when it contains that flammable Hydrogen.

So we decided to try separating hydrogen and oxygen from water through Electrolysis.

Hydrogen is released by the minus pole, also called the cathode.
Oxygen (oxygen) is released at the plus pole, also called the anode.

Electric-motor model, compas with three wires across it, Ørsted

We placed a compas on a wooden board. Pulled a wire across it with a circuit breaker/push button, so we could turn on and off the power. We then pulled two more wires more than 120⁰ apart (evenly distributed), also with a  circuit breaker/push button. We then pushed the buttons alternately, so that the magnetic field changed, and thereby made the compass needle turn around. This is electromagnetism, as Ørsted discovered in 1820. It is used  in most electrical appliances we use every day.

We also were so lucky that my dad had a old electric motor model we could test with and examine a coil and a iron core.