Circular Motion Videos by CB Tung

Go to this link and watch the video about centripetal forces on the Space Station!

nwsphysics99 — 2015-02-25 20:02:07 UTC

http://www.pbslearningmedia.org/resource/npe11.sci.phys.maf.centripetal/teaching-from-space-centripetal-force/

Then return here and comment specifically on something you learned from the video.

Amir

2015-03-01 17:38:57 UTC

centripetal force causes liquids to organize by density as they show with the bubble in the space tea

Steven

2015-03-01 21:42:42 UTC

Centripetal force forces the air bubble in the tea bag to concentrate in the middle and form a big circle because air has less density than liquid. As the tea bag is rotating, the centripetal fore pushes the air to the middle while pushes the liquid to the side.

Jack

2015-03-02 00:53:45 UTC

I learned that the air bubbles remain in place due to weightlessness. Gravity usually drags

more massive objects like liquids to the bottom of a bag, but in this case, there is no gravity,

so the bubbles remain in place.

When spun, the tea bag creates a central bubble of air in the middle, due to the (massive)

liquids being forced to each end of the bag. (Is this the theory behind gravity generators in

sci-fi movies like Interstellar?).

alex

2015-03-02 06:14:35 UTC

when the tea bag was spun the centripital force sent the tea to the edges which made the air create a circle. I can now totally see that physisits are much more deserving to go to space just because of the amount of fun they would have. He seemed like he was having more fun than most people would.

Riley H

2015-03-02 06:25:01 UTC

I learned that the centripetal force in the spinning water bubble causes it to change shape so it isn't spherical anymore, but more of an oval.

Fiona

2015-03-02 06:37:36 UTC

I thought it was really cool that the reason air bubbles rise to the top on earth is because they're less massive than the tea, so in space if the bag of tea is spinning because of centripetal force they go to the middle because they have less mass than the tea.

Harrison

2015-03-02 07:14:24 UTC

The centripetal force in the tea bag experiment oriented the air bubble in the middle of the revolving bag because in the absence of gravity, the densities of the substances were sorted as the tea was pulled to the outside and the air was forced to the center.

Danny

2015-03-02 07:33:35 UTC

I really want to know what the metal thing was used for when they walk in space.

Anyway, I do curious that whether the bubble in the tea bag was gathered in middle because of centripetal force or the centrifugal force.

I think it was because of the tea actually spun out and pushed the air bubbles into the middle zone and created a big round bubble.

Carrie S

2015-03-02 14:29:58 UTC

I thought the part of the water demonstration where the bubble spits into three was interesting because the two parts that left the center bubble were at approximately right angles to each other. I'm not sure if the angle was a coincidence related to what the guy was doing with the dental floss, but it reminded me of the roller coaster demonstration where the video described what would happen went flying off the tracks during the loop.

Forrest Henry

2015-03-02 16:28:59 UTC

I learned when something in space starts spinning, it doesn't stop, applying a constant force that needs no extra force. It makes sense that any movement would require energy, but centripetal force does not. If the space station were a true vacuum, any of the things that Jeff had set spinning would have never stopped, and would experience constant acceleration with no other outside force. That's pretty neat.

Evan

2015-03-02 17:13:31 UTC

In zero gravity the centripetal force applied when liquid with bubbles rotates forces the air

to the center of the container.

andrew

2015-03-02 17:15:31 UTC

I found it interesting that once motion is set into place in space,

no external force exists and motion never stops, the object

will continue to move at a constant acceleation.

Seamus

2015-03-02 17:25:16 UTC

I learned that they have tea up at the ISS. I also learned that if said bag of tea is spun, the air bubbles inside will coalesce to the center of the bag due to centripetal force and the bubbles having less mass and being less dense than the liquid around them. It also looks insanely cool and I want to be an astronaut.

Adam

2015-03-02 18:07:47 UTC

We think about bubbles rising to the surface of liquids when we talk about density. But, in reality, bubbles are forced away from the direction of acceleration. On earth this means the bubbles go up, but when the liquid is "feels" like it is being accelerated outwards, the bubbles gather in the center. I hadn't thought of that before.

Henry

2015-03-02 18:19:27 UTC

The tea was a really interesting demonstration because centripetal force making the bubbles coalesce in the center sort of "replaces" gravity. He said that on Earth, because the tea is more dense, it would "get in the way" of the bubbles, pushing them to the top. That also reminds me of Rendezvous with Rama, a science fiction book by Arthur C. Clarke that involves a giant vessel that spins, simulating gravity for its occupants.

Jacques

2015-03-02 20:17:35 UTC

I expected the water bubble to form into a disk shape as it was spun, but instead it spit into smaller water bubbles as the force of the surface tension holding the bubble together was exceeded by the centripetal force.

Hawi

2015-03-03 04:17:41 UTC

I leanred that the tea in the bag goes to the outside while pushing the air into the center of the bag because the air has less density than the liquid.

Sam C

2015-03-03 17:51:53 UTC

I learned that planets and moons

act with centripital force but this was

not explained in much detail so i would

like more information about that. I really

liked the example of the tea in the bag to explain

how this force works though.

Chloe Q

2015-03-03 17:55:43 UTC

I learned that the centripetal force was acted on the tea bag to make the less denser air congregated to the center of the tea bag and the denser tea was spread out the bag.

Evan L

2015-03-03 20:13:20 UTC

I learned from the tea bag demonstration that centripetal acceleration created centripetal force at the center of its rotation and attracted substance with less mass which was air.

Max Deckman

2015-03-03 21:02:54 UTC

I learned that planets and moons also

use centripetal force to revolve around

the sun or other planets. My favorite

part of the video was when he spun

the tea and the air bubble formed in

the center of the bag

Taishi Ozeki

2015-03-03 21:05:43 UTC

The rotation of planets such as sun and moon uses centripetal forces. Also when the tea bag was spun, all the air bubbles when to the middle since air has less mass than the liquid.

Alejandro

2015-03-03 21:17:24 UTC

I learned you can spin a bubble of water around with a piece of floss in space