imported>Stwikiadmin: Created page with "== Age == Elementary School,Middle School,High School == Format == Stage Show,Hands-on == Scientific Concepts == Angular momentum and conservation of momentum == Materials ..."

2013-09-11T02:18:08Z

Created page with "== Age == Elementary School,Middle School,High School == Format == Stage Show,Hands-on == Scientific Concepts == Angular momentum and conservation of momentum == Materials ..."

New page

== Age ==

Elementary School,Middle School,High School

== Format ==

Stage Show,Hands-on

== Scientific Concepts ==

Angular momentum and conservation of momentum

== Materials ==

Small dumbbells
Spinning chair
Bike wheel on mount
Also see chart attached to box!

== Safety Precautions ==

Science Theatre demonstrators must keep the safety of themselves and their audience in mind at all times. All Science Theatre demonstrators must have read through the Safety Training page. The ST Safety Box with first aid kit, fire extinguisher, etc. should always be available to demonstrators. Always wear safety gloves, glasses, and a labcoat if handling chemicals; always perform potentially dangerous demonstrations at a safe distance from the audience; and always keep a very close eye on any volunteers you call from the audience. Dizziness and potential flying weights. Don't spin kids too fast and keep a small radius clear of viewers in case weight gets dropped.

== Preparation ==

Sturdy ground and a couple of volunteers

== Demonstration ==

After the intro talk, have a volunteer sit on the chair. Have the seated volunteer hold one weight in each hand. While spinning, have the volunteer slowly extend their arms outward with the weights. Observe decrease in revolutions per minute. Bring weights back in. Observe increase in revolutions per minute. Stop Chair and discuss observations. Have another volunteer sit on chair. Spin the bike wheel and hand it to the volunteer vertically. Have the volunteer move the wheel so it is horizontal. Observe that the person starts spinning. Have the volunteer switch the wheel's rotation (flip it 180 degrees). Observe the chair slow, stop, and revers. Have the volunteer return the wheel to its upright position, take wheel from the volunteer and have them return to their seat. Stop wheel and discuss with observers.

== What to Say ==

Start by discussing momentum in linear paths.
Example. "So have you ever noticed how things are moving tend to be very hard to stop? This property of matter is call inertia or momentum, a body's ability to resist change in motion. Momentum, quantitatively, is the product of mass and velocity, So a heavier thing moving quickly will have much more momentum than something lighter moving at the same speed."

Explain conservation of momentum.
Example. "So you guys know that mass is conserved in systems right? If I take a 5 kilogram weight and break it into pieces, all the pieces will add to be 5 kilograms. Well, the same goes for momentum. If a system of several objects has a certain amount of momentum, it will always maintain that same amount of momentum - even if it gets redistributed amongst the objects in the system. External forces like friction and air resistance can change the amount of momentum in a system."
You can use the example of a simple collusion between billiard balls, where momentum is transferred and conserved. Note that this type of momentum is 'linear' momentum - the balls move in straight lines.

Relate momentum and its conservation to rotational system. \\ Example. "So we understand how momentum works in straight lines right? Well it works the same when things spin too. Something at a certain speed, measured in RPMs, will keep that speed unless something comes to take it away. Now, with things that rotate we have a couple other nest things with momentum. For instance, the distance away from the axis of rotation (what the object spins around) can change the way things rotate. Specifically, we'll talk about moments of inertia. That's a big physics term that basically says, 'for round objects, the farther away from the middle the weight is, the slower it will want to move.' So a hallow ball will spin much slower than a solid ball if they have the same mass."

Bring out the chair!
Example. "So I've got a little demo here to help you guys see momentum in action. Let's pretend this chair is an isolated system. (Get two volunteers and lean their names) SO I'm going to have (Volunteer 1) sit here on the chair and spin. Look at him/her go. Now assuming nothing comes along to stop her, (Volunteer 1) will spin like this forever and ever. But we like (Volunteer 1) so we'll let her put her feet down to stop. Now, to show you a little about those 'moments of inertia' I'm going to give (Volunteer 1) a couple of weights. Careful now, they are weights. Ok, so let's start off with weights clase to you. (Start spinning) Ok, now what I want you to do is slowly take the weights and bring them outward. Ok, bring them back in, and now back out again. Did you guys notice anything? That's right, she slowed down. That's why whenever people spin quickly they try to curl up as tight as possible, like figure skaters or divers."

"Ok (Volunteer 1), thank you very much you may go back to your seat. Let's hear it for (Volunteer 1)! Alrighty, for my next trick, I will have (Volunteer 2) sit on the chair without spinning it. Remember how when (Volunteer 1) brought the weights out the chair slowed down? Well this next part will show this property more clearly. So I've got this bike wheel here and it spins. Now what I'm going to do is start it spinning and hand it to (Volunteer 2) here vertically. Notice that the wheel is spinning vertically and (Volunteer 2) is stationary - no part of the system is spinning in the horizontal direction! Ok (Volunteer 2), turn the wheel now to one side. Now the wheel is spinning horizontally in one direction. Since the original system was not spinning horizontally, by conservation of angular momentum, the systems should never spinning horizontally! That's why (Volunteer 2) starts spinning horizontally in the other direction - to cancel out the spin of the wheel. Ok, now turn it over to the other side. For the same reason, (Volunteer 2) starts spinning in the other direction. Pretty cool stuff eh?"

Feel free to insert additional life examples where ever you see fit.

== Why It Is ==

Momentum is conserve in any isolated (closed) system, where there are no net external forces acting (i.e., no friction, gravitation, etc.). This is a fundamental property of the natural world (a law of physics).
Additionally, a neat tid-bit is that Newton derived his second law for momentum. That is , "forced is the rate of change of momentum" is equivalent to 'F-ma.' So Newton's third law is really describing the conservation of momentum, that the interaction of objects yield equal and opposite reactions and thus no net change of momentum.

== Real Life Examples ==

Figure skating, divers, anything that spins

Angular Momentum Chair - Revision history

imported>Stwikiadmin: Created page with "== Age == Elementary School,Middle School,High School == Format == Stage Show,Hands-on == Scientific Concepts == Angular momentum and conservation of momentum == Materials ..."