Newton's Laws Quickies

Uncle Newt's Laws Quickies

The following are real quick, most less than a minute, demos to be used either as stand-alone individual demos or, as I used to do them, as rapid fire demos that will get the kids involved quickly. The last ten years or so, I've combined all these demos into one large inquiry lab for the kids to conquer. The image below shows my classroom set-up ready to go with 22 lab stations. Each station contains one of the 'demos' listed later. Each pair of kids has to wonder around the room and observe, think (a painful thing for most kids...), take a few measurements, and apply what they saw or did to one or more of Uncle Newt's Laws. Feel free to adapt these for your use. I set this up as full inquiry. No instructions at all. Most of the stations simply sate, "Play and report". Kids have a blast with this. My 22 stations are completed in 2 one-hour sessions, then they have to write up explanations in a semi-formal report.

I'm guilty of what some purists refer to as animism, placing animate properties on inanimate objects. Guilty as charged. Get over it.

NOTE: Include (Coming Soon... I forgot...) 7. Tablecloth Trick 8. Tug-O-War 9. Spinning Candles / Horizontal floating 10.

Hey, You just HIT me!

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(This one is an exciting painful demo, so word to the wise... This is one I do only once per class group; it hurts. Feel free to use the video if you are a scardy-cat...) Have a kid break a meter stick over your forearm (get the idea I enjoy pain?). If you don't want to use your arm, use the edge of the classroom door or some similar thing. Kid swings like an overhead Ax blow to firewood so that contact is made around the 50-cm mark and on the FLAT edge of the m-stick. If it's your arm, stick breaks and kids go, "Ooooo". Safety Note: Have all kids within a few meters of you wear goggles. Maple meter sticks sometimes shatter and splinters fly around. Cool effect, but you really don't want to hurt your kids, do you? Too much paperwork... If it's another m-stick instead of your arm, hold it so it is vertically aligned - this allows his stick and yours to be perpendicular. Good example of the property of inertia. The 50 cm mark of his stick is 'told' to stop, but the end of the stick isn't told that, so it continues to move fast. What happens to wood when one part is told to move and another isn't? SNAP!

Hey, You just HIT me, PART 2! I do this one all by my lonesome at the front desk. There's just something about one of my students swings a hammer at my hand while it's flat on the demo desk that scares me. Call me a chicken, but...
Just like the meter stick thing above, this is cool! Obtain a brick. A regular red construction brick works. I use the grey landscaping bricks since I have a batch left over from a job I was supposed to do in my back yard...I'll get to it...tomorrow... Anyway, lay the brick on your hand or forarm which is flat on the desk top. Smack the brick HARD with a hammer. The brick breaks in half, the kids go, "OOOooooo", and you are absolutely unharmed. Why?
Just like the cinder block broken on my chest while on a bed-O-Nails, see Bed Of Nails Demo, the brick has lots of inertia and wants to stay stationary. The hammer, which also has lots of inertia, is telling the brick to get out of the way. The brick says, "NOT!" and stays put. However, the force from the hammer causes deformity and the brick snaps - usually in half right around your hand or arm. Cool.

Wet Relay Race This will demo that even liquids have inertia. Two teams of two kids each to have a simple relay race. Distance is about 10m. They must run to the determined point, usually another student standing there, run around the point, return to his/her partner and "tag" off so the 2nd person can do his race. However, they must carry with them a FULL beaker of water! The more they spill, the more points they lose. I give 5 points to the winner, 3 to 2nd place, and 1 to the 3rd - LOSER! Then I deduct a point for each 10 ml missing from the FULL TO THE BRIM 500 ml beaker. Most often, the winner even has a negative score.
This shows the "sloshing" of liquids, like coffee in a car ride, is just a result of it's own inertia telling it to stay put while the mug chnges velocity! The kids then have to explain where they lost the water and why.

Doll Fight!

Use dolls or stuffed animals (I use original Cabbage Patch^TM Dolls) to demonstrate the physics of a seatbelt - INERTIA. Have one hop on a dynamics cart, or roller-skate, and head down a ramp that has a large brick wall (cinder block) at the bottom. Upon the cart hitting the wall, the cart stops, but the doll continues and is 'hurled' over the wall and the cliff (my desk edge, actually). I make this a little more interesting by have a rogue asteroid, a one-kg mass, come by and hit the defenseless doll while prone helpless on the floor. The other doll had physics and straps on his seatbelts. In this case, lots and lots of duct tape. Upon smashing into the wall, he/she is still a part of the object and is thus saved the ignoble end of cliff flying. This leads nicely into seatbelt safety. Your better kids will make the connection. This is a good thing.

Boring / Exciting mass

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: Sit a large mass on the table. Have kids explain it in terms of Newt's Laws. It just sits there. They can't touch it. Covers all 3 Laws.

Thought Experiment : Have kids explain this classic typed on paper and just taped to desk as a station. A rich merchant finds himself stranded in the middle of a frozen lake. Don't ask how he got there. Think Twilight Zone... The surface is perfectly frictionless. All he has is his clothing and a large bag of gold coins. How can he save himself? The answer is to toss the bag. Due to NL3, he will slide backwards. He can them walk around the lake to retrieve his gold.

Stomp Rocket ^TM

These are so kewl! Have kids play. They'll have a ball and invariably get this wrong. They aren't "rockets". They are, however, based on NL2. The air forced through the bladder causes the 'rocket' to accelerate forward. Period. Rockets operate on NL3; thrust FROM THE ROCKET equals forward force. These can be purchased many places. WalMart has them cheap from time to time. Educational Innovations here in CT has them all the time.

Water Rocket

These are so kewl! Have kids play. Outside... They'll have a ball and invariably get this wrong, too. These are "rockets". They are based on NL3. The air forced air forced into the bottle will force water out the neck when released. The water 'shooting' out one way causes a reaction force in the opposite direction that propels the bottle forward. Educational Innovations here in CT has them all the time. You might even want to think of having a rocket competition where the kids design their own rockets. Stabilizers and couterweights and such. Incredible designs can come from these.

Mickey^TM Ears

This came from somewhere long ago; maybe a Hewitt thing. Make a pair of hanging "ears" from a wire coat hanger and two balls of modeling clay. Bend the wire into a large "M" shape where the clay balls, attached to the ends, hang lower than the center. Balance this silly-looking contraption on your head. Now, turn 180^o quickly! The 'ears' stay in place while your head turns under them. The clay balls have alot of inertia and tend to stay in place.
Why do I call them Mickey ears? Ever see Mickey Mouse? His ears are always in full view no matter where his head is facing. This means his ears are the most massive part of his body and stay in place while his body moves under them. Kewl!

Use NFL Football clips to show that the heads of the Q-backs actually DON'T get snapped back when tackled. The head actually stays there while the rest of the body is pushed out from under it. Same injury, just not caused the way they think.

Card-N-Coin:

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I do this using a beaker, index card, and penny. You can purchase a specific set-up for about $30 from any science supply house, but why spend money... Place the card on top of the beaker with the penny on top of the card in the center of the beaker. Flick the card out as fast as you can. The penny will drop into the beaker. Why? Inertia. This also moves into NL2 & NL3. NL2 as the force of your finger caused the card to accelerate away. NL3, which can be applied to most of these, as the card fights back against your finger. I stick with the primary Law.

Tug-O-War

Using a 100' rope, I pit my entire class against another Fizzix class, usually just a challenge that sort of happens during classtime. (Sometimes, the other teacher gets ticked about the interruption, but he gets over it...). Prime example of NL3. Kids have to understand the tension in the rope is the same everywhere in the rope, spo both teams feel the same force. To add a little excitement, I even have an in-class round-robin type contest 2-on-2. Kids love it.

Balloons!: Have kids blow up regular cheap balloons and let them go. NL3; rocket operation. Air one way, balloon the other.

Hoop-n-Marker:

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I got this one from Amy Durden of Savannah Christian Preparatory School, Savannah, GA. It's a cool twist on the ole Card-N-Coin trick above. In her words -
Buy an embroidery hoop at Walmart for 64 cents. It's 10 inches or so in diameter. Buy and drink a fruit drink in a bottle. The opening should be a little more than an inch. I like Mystic or Fruitopia. Any flavor. Grab a dry erase marker. Balance the inside circle of the hoop (discard the outer ring) on the open mouth of the bottle and the marker on top of the hoop. (hardest part of the demo) Yank the hoop out from under the marker (fast and straight sideways) and the marker will fall into the bottle 10 inches below. My kids think it's SOOO cool. It's easier to see from a distance than the index card and nickle trick I used to use. If you like the trick, buy several hoops because they break easily.
Thanks, Amy!

Totem Poles or Hammering Studs:

I am horrible at this, but the kids can do it. I found two little wooden totem poles somewhere in my journeys. I've tried to locate them online, no success.

[UPDATE 06/26/2012: Just received words these ARE indeed available online via eBay! Michael Gilpin from the Bronx, who attended one of my workshops sponsored by KIPP NYC and Google™, found them! Hold onto your hats and fasten your seatbelts. I've been trying to find these bad boys for years to no avail. I've been searching for "Totem Pole Toys" and "Wood Stick Hitty Thingee" and other very descriptive names. No wonder. The real name of these kids is, "Japanese Daruma Otoshi Bodhidharma Wood Stacking Striking Hammer Game"! Obvious to the most casual observer! Just copy that long dern name into your browzer and you'll find a few places that sell these: $4.99 for the small ones and $40+ for the big boys. Here's a Tiny Url (TinyUrl.com) to the eBay™ site I found via Michaels' info: http://tinyurl.com/7d37tzh . Thanks, Michael!]

They consist of 5 wooden discs with a wooden hammer. Kids LOVE this one. The object is to knock one of the lower ones out and have the others drop straight down to take its place. Kids actually make a competition out of it. If you can't find these things, place 3 or 4 hunks of 2x4 stud wood on top of each other on your lab desk. Smack the bottom one, going in the direction of the long side, smartly with a hammer. Note, the bottom one moves out of the way while the others above just drop down in place in a pile. Cool.

Roller Skating with The Fat Guy: This is always fun for me. This works BEST with a volunteer or two bringing in their inline skates. Otherwise, just use some sturdy collision carts that will hold a kids weight - I have some of those old wooden ones that even hold me. These demos can also be done in conjunction with Newt's 2^nd and 3^rd Laws.

1. While a SMALL kid (to me they are ALL small...) stands in front of you with skates on both you and the kid, push on the kid's shoulders with enough force to cause motion. BE CAREFUL, small children sometimes don't need lots of force to fly across the room! Note, the kid moves backward a much larger distance than you. Keep in mind, I am 250-ish. Most of my kids are in the mid 100's. This works for me all the time. If you are on the small-ish side, pick a LARGE kid and YOU move, not him. Same effect, different direction.

2. Do this in reverse IF the kid and you (or two kids, if you choose.) are OK skaters. Head toward each other with enough speed to actually notice a change. It doesn't have to be blazing speed, but fast enough to note a change in speed when you collide. Grab onto each other upon contact. Note, if the mass difference is large enough and the speeds were the same, the "group" now moves in the direction of the larger person. The little guy got "gobbled up".

HOVERCRAFT

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I use a home-made hovercraft, see my hovercraft page, to demo 1st Law. This is absolutely GREAT due to the "lack" of friction and it's actually quite dramatic! One kid floats on the hovercraft while another tosses him my 35 pound (yes POUNDS) medicine ball. When the hovercraft kid catches it, he and the craft move backwards. NL3. Now, have the hovercraft kid through the medicine ball to the 1st kid. The hovercraft kid STILL moves backwards! Again, NL3. Kids have a heckuva time explaining the same result even though the ball went two different directions.

Wile E. Coyote: I use video clips extensively. Here, you can pick just about ANY cartoon to show what DOESN'T happen. Wile E. Coyote, that persistent carnivore from the desert, disobeys Newt's 1^st Law vertually all the time.
Also, don't forget the movies! For Newt's 1^st Law, one of the good clips is from Star Trek IV, The Voyage Home. This is the one where the ONLY true Star Trek crew has to go back into the past - OUR current time - to pick up some whales to save the world of the future. Silly storyline, I know, but still a good flick. Toward the beginning of the movie, this huge alien probe is sucking all the EM energy out of space ships and satellites as it passes. There is a scene where two shuttles are flying thru space, lose their energy - lights go out and the engines stop (I know, you HEAR them...) - and come to a screeching halt!
This blatantly disobeys Newton! The shuttles would still move forward in a stright line at their last speed. Why can't these Hollywood guys call me for consultation work? See my Hollywood Science site for more ideas.

Crash Test Dummy Videos: Obtain a video or DVD of crash testing. These can be obtained free from many sources. Show in SloMo the inertial effects of the passengers AND even the car parts during a crash. I even make this a relevent "seat belt safety" tie-in.

Cart & Mass : Typical FMA demo. Attach a string to a wheeled cart. Run this string over a pulley at the edge of the desk. Not to worry, if you have no pulleys, just use the edge of the desk itself. From the other end of the string, hang a weight. [It's a nice idea here to hang an actual mass 'hanger'; a hooked thingee that will allow you to stack up weights so you can change the hanging mass. Devise something that works for you and your equipment. A simple large paperclip and washers will work in a pinch. The string should be just as long as the table is long (or side). Two demos to do:

Vary the hanging mass but keep the carts mass the same and record the motion of the cart when the hanging mass is released. You should notice that with larger masses, the cart accelerates more.
Vary the mass of the cart while keeping the hanging mass constant. This can easily be done by simply taping or stacking masses on the cart on the table. You should notice that the acceleration of the cart decreases as the mass of the cart increases.

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