Physics Olympics....

[sao123]

Ok so my little brother is in 12th grade physics, and every year they have this 3 event competition. they didnt do this when I was in HS, so it has my curiosity sparked.

can anyone give me some insight how to accomplish the following....

Event 1:
Build a vehicle which is powered only by a standard mouse trap. Car which travels the farthest wins.
i was thinking about this, and i dont think extenting a pole from the trap, with a long string wrapped around a wheel is the best solution.

Event 2:
Build a barge by folding an 8in x 8in piece of foil. Barge that floats the most pennies wins.

Event 3:
Build a device which will protect an egg from a 2 story drop. Parachuting not allowed.
the egg must land without breaking.



I think this is gonna be a fun weekend.

 

[DrPizza]

I was introduced to this contest at Buffalo State's summer physics teacher's institute (I highly recommend the program to anyone entering physics teaching or who has only taught for a few years)

We do several events throughout the year now. One of the standards is engineering design. Many teachers ignore it because it's not assessed on the state exam. I no longer ignore it... it's another thing that makes the course more fun.

Other events I've done:
Stack a certain number of bricks - only 1 brick can be the base (no other bricks touching the floor.) Group whose stack extends the farthest horizontally wins.

Construct an airplane from tape, straws, and tissue paper. (this event was a flop - or rather, every single plane flopped. I won't do it again in the future)

From ONE sheet of regular copy paper, build a tower. Tallest tower wins. Materials: 1 sheet of paper, a couple pairs of scissors, about 2 feet of tape. Record tower in 30 minutes was just over 2 meters. I've seen much taller from a single sheet of paper.

Slight deviation on your event #3, the egg drop:
We start at 1 meter, move to 2 meters, then 3 meters, then 4 meters, then 5 meters, 7.5 meters, 10 meters... up to the limit we have at our school. The egg is not surrounded by a device, but rather, the built device has to catch the egg without breaking it. I've seen the contest scored by the quotient of the height dropped and the height of the device. To make it simpler, I just limit the height of the catching device to about a foot. Materials are somewhat random, but usually some string, tape, a few pieces of paper (including the instructions), straws, manila folder, a styrofoam cup or two, and maybe a few other things that I have laying around.

At the lower heights, there is one glaring engineering problem that is often overlooked: the egg survives the impact with the device, but then it bounces up, out of the device, and onto the floor where it cracks. It doesn't have to go up too far to break when it hits the floor - 6 inches is sufficient - so, even rolling off the top of the device sometimes results in a cracked egg.

I'm proud to say I built a device (out of a manila folder, a couple pieces of string, a styrofoam plate and cup, and masking tape) which will catch an egg without breaking it from an unknown height. It survived 4 or 5 stories with no problem, but we missed the device when we dropped it down the stairwell from the top floor (6th floor?) Since aim isn't supposed to be a factor, a plumb bob is suspended next to the "drop zone" for everyone to use in lining up their drop. Unfortunately, the plumb bob was touching something which pushed it out of alignment on our final drop. I calculated, based on the way the device worked, that the device would successfully save an egg dropped from about 12-13 stories (as long as the egg hits the device.) If the egg reaches terminal velocity at that height, then the height is pretty much unlimited (again, as long as the egg hits the device.)

Tomorrow in class, and the next few lab periods, my class is starting their final competition: build a rocket (powered by a 2 liter bottle filled partially with water and compressed air to 100 psi) that will launch an egg into the air. The egg that's in the air the longest, without breaking, wins. Actually, I calculate the winner this way: time in the air, multiplied by 2 if the egg doesn't break. Thus, if everyone's egg breaks, the last group can't win simply by having their rocket tip over. (t = 0.01 seconds) Then, if someone figures out how to get the rocket to go up 5 thousand feet (actually, that height probably isn't possible - conservation of energy), then they deserve to win, even if their egg breaks. Winning times are around 30-40 seconds. It's damn near impossible for them to design parachutes that work effectively. (or rather, they overlook how critical this aspect is) Parachutes - maybe they make a perfect parachute, but it's TWO parts that matter: 1. The parachute descends very slowly with the egg in some sort of capsule. 2. (more important) The parachute actually deploys. Model rockets: an extra charge that goes bang, ejecting the parachute after a certain period of time. These rockets: no explosive devices allowed. Deployment of parachute is quite a challenge.

 

[kleinwl]

The most important part of winning the car competition is reducing the friction and mechanical losses of the system... so a string around the wheel is right out. A gearing system, like on a bicycle, would help the mouse, since the torque that he provides will be fairly low. A chain drive, will also limit the slippage (and thus losses) from the transmission of energy from the mouse to the wheel. Since it does not seem to matter how fast the car is, I would gear for high torque (low effort), with 2 wheels engaged (to limit torque steer).

For the barge float (assuming stagnite water) design your vessle to maximize displacement (thus boyancy). Also, while loading the vessle, equalize the load (to the max extent possible).

The egg drop is an interesting challenge, since eggs are very resistant to pressure. If the pressure is equalized across the shell, the egg will never break. I've always wanted to try dropping the egg in a simple waterbottle that is loaded with foam (or other viscous) material (pressurized). As long as the waterbottle does not fail, the egg should not have any trouble.

About the parachute, why don't your students apply a "packed" parachute to their egg with a line (like the military does) so that at maxium height, the line pulls open the parachute, allowing the egg to float downwards?

 

[DrPizza]

re: the egg in the foam.
I put an egg in a shrink-wrap bag so that later I could more easily extract it from the foam.
I then inserted it diagonally into a cut open 2-liter bottle and encased it with "Great Stuff" foam (relatively strong, dense foam sold in hardware stores)
I gave it the 24 hours or whatever it was to cure.

It took one heckuva beating. Kicked it all over, spiked it on the floor, and the egg survived. Eventually, after a pretty decent amount of effort, we got the egg to break.

Here's a better idea than the foam:
put the egg in a highly dilatent viscous "fluid". Dilatancy: the phenomenon whereby a viscous fluid becomes a solid under pressure.
It's like encasing it in a liquid that becomes concrete upon impacts. We didn't test it; we had an egg survive one incredible impact though.. I'd estimate an egg could survive in it when impacting a brick wall at 150mph, depending on the orientation of the egg.

edit: I believe if you start mixing corn starch with water, you can create such a fluid. Slowly add corn starch until it gets really really thick. If you punch it, it will solidify, then when you remove your hand, it will become liquid again. Cool stuff. I wish I could remember what we used in ceramic engineering (not that you'd easily be able to get the stuff)... the tile company I worked at for a while used it as one of the main ingredients. I taught the others in the lab how to play with the stuff... you could make a relatively smooth easy flowing fluid, fill a bucket half full of the stuff, swirl it around to show someone it was a liquid, then quickly dump the bucket over them. The "fluid" would instantly solidify under the stresses and nothing would come out of the bucket... magic!

 

[AbsolutDealage]

Originally posted by: DrPizza
depending on the orientation of the egg.

It is almost impossible to break an egg stressing it from end-to-end. If you could guarantee the orientation of the egg upon impact, you could probably come up with a very durable solution.

 

[silverpig]

Originally posted by: DrPizza
re: the egg in the foam.
I put an egg in a shrink-wrap bag so that later I could more easily extract it from the foam.
I then inserted it diagonally into a cut open 2-liter bottle and encased it with "Great Stuff" foam (relatively strong, dense foam sold in hardware stores)
I gave it the 24 hours or whatever it was to cure.

It took one heckuva beating. Kicked it all over, spiked it on the floor, and the egg survived. Eventually, after a pretty decent amount of effort, we got the egg to break.

Here's a better idea than the foam:
put the egg in a highly dilatent viscous "fluid". Dilatancy: the phenomenon whereby a viscous fluid becomes a solid under pressure.
It's like encasing it in a liquid that becomes concrete upon impacts. We didn't test it; we had an egg survive one incredible impact though.. I'd estimate an egg could survive in it when impacting a brick wall at 150mph, depending on the orientation of the egg.

edit: I believe if you start mixing corn starch with water, you can create such a fluid. Slowly add corn starch until it gets really really thick. If you punch it, it will solidify, then when you remove your hand, it will become liquid again. Cool stuff. I wish I could remember what we used in ceramic engineering (not that you'd easily be able to get the stuff)... the tile company I worked at for a while used it as one of the main ingredients. I taught the others in the lab how to play with the stuff... you could make a relatively smooth easy flowing fluid, fill a bucket half full of the stuff, swirl it around to show someone it was a liquid, then quickly dump the bucket over them. The "fluid" would instantly solidify under the stresses and nothing would come out of the bucket... magic!

My team came damn close to winning the physics olympics when I was in HS... and I was only in grade 11 (got screwed over on 2 events though.. still came top 5 out of like 100 teams... oh well).

I immediately thought of the dilatent fluid for the egg. Not only does it have a great chance of winning, but the coolness factor of being probably the only team to do it this way would definitely garner some points. It'd be even better (maybe even necessary?) to make your fluid have the same density as the egg so it can sit suspended.

The mousetrap one is all about simplicity. Keep it simple, keep it LIGHT, and keep it efficient. Reduce friction wherever you can.

 

[Howard]

Dilatent, is that synonymous with non-Newtonian?

 

[TuxDave]

Originally posted by: DrPizza
re: the egg in the foam.
I put an egg in a shrink-wrap bag so that later I could more easily extract it from the foam.
I then inserted it diagonally into a cut open 2-liter bottle and encased it with "Great Stuff" foam (relatively strong, dense foam sold in hardware stores)
I gave it the 24 hours or whatever it was to cure.

It took one heckuva beating. Kicked it all over, spiked it on the floor, and the egg survived. Eventually, after a pretty decent amount of effort, we got the egg to break.

Here's a better idea than the foam:
put the egg in a highly dilatent viscous "fluid". Dilatancy: the phenomenon whereby a viscous fluid becomes a solid under pressure.
It's like encasing it in a liquid that becomes concrete upon impacts. We didn't test it; we had an egg survive one incredible impact though.. I'd estimate an egg could survive in it when impacting a brick wall at 150mph, depending on the orientation of the egg.

edit: I believe if you start mixing corn starch with water, you can create such a fluid. Slowly add corn starch until it gets really really thick. If you punch it, it will solidify, then when you remove your hand, it will become liquid again. Cool stuff. I wish I could remember what we used in ceramic engineering (not that you'd easily be able to get the stuff)... the tile company I worked at for a while used it as one of the main ingredients. I taught the others in the lab how to play with the stuff... you could make a relatively smooth easy flowing fluid, fill a bucket half full of the stuff, swirl it around to show someone it was a liquid, then quickly dump the bucket over them. The "fluid" would instantly solidify under the stresses and nothing would come out of the bucket... magic!

Or... you can put the egg in a can of marshmallow cream. That thing will make the egg invincible.

 

[jagec]

Originally posted by: sao123
Ok so my little brother is in 12th grade physics, and every year they have this 3 event competition. they didnt do this when I was in HS, so it has my curiosity sparked.

can anyone give me some insight how to accomplish the following....

Event 1:
Build a vehicle which is powered only by a standard mouse trap. Car which travels the farthest wins.
i was thinking about this, and i dont think extenting a pole from the trap, with a long string wrapped around a wheel is the best solution.

Event 2:
Build a barge by folding an 8in x 8in piece of foil. Barge that floats the most pennies wins.

Event 3:
Build a device which will protect an egg from a 2 story drop. Parachuting not allowed.
the egg must land without breaking.



I think this is gonna be a fun weekend.

"think outside the box!"

For the mousetrap...does it say the vehicle has to be fully contained? Put the mousetrap on a "base" separate from the vehicle, put a REALLY LONG wire at the end with a string attached. When the mousetrap gets activated, it will pull on the string, which is attached to the vehicle. If you design it correctly, it will roll MUCH farther than the competition.

For the barge, yeah, maximize displacement while minimizing material waste. Try to avoid making a square boat (wastes a lot of material)...maybe just crimp two edges together and balance the load to prevent collapse?

For the egg drop...it says no parachutes, but does it mention autorotation? I think not! That is the #1 winning strategy at these competitions, since a successful design will work just as well from 5,000 feet as from 5 feet. Just cut a big circle out of cardboard, cut a couple slats in it, and bent a bit of it up to give it a direction. Then suspend the egg from teh middle with a bit of styrofoam to protect it.

 

[Calin]

No. 2 - origami, boats made of paper
No. 1 - make a rocket and use the mousetrap as a roman catapult (as seen in Gladiator)
No 3. Fill the egg with wax, use a duck egg (much stronger than chicken eggs)

 

[TStep]

I never did this but:

Event 1: Does it have to be a car? Can it be launched?

Event 2: a sphere would displace the most h2o per surface area, so would not 1/2 a sphere be the most viable solution? It would provide more rigidity and stability in the water than a flat solution. Would have to be made with folded ribs I would presume.

Event 3: I'm not sure, but I think an egg is strongest when the force is applied axially to the top and bottom. Do not apply force to the side. So a device comprised with this in mind and weighted such that it would land in this configuration. Also, what about greasing up the egg, then encapsulating it in spray foam? I'm not sure what your rules are.

 

[DrPizza]

Originally posted by: TStep
I never did this but:

Event 1: Does it have to be a car? Can it be launched?

Event 2: a sphere would displace the most h2o per surface area, so would not 1/2 a sphere be the most viable solution? It would provide more rigidity and stability in the water than a flat solution. Would have to be made with folded ribs I would presume.

Event 3: I'm not sure, but I think an egg is strongest when the force is applied axially to the top and bottom. Do not apply force to the side. So a device comprised with this in mind and weighted such that it would land in this configuration. Also, what about greasing up the egg, then encapsulating it in spray foam? I'm not sure what your rules are.

for greasing it up and encapsulating it in spray foam, I'd just go with putting it in a little shrinkwrap baggie and encapsulating it. However, spray foams take quite a while to cure. Usually in these contests, the egg is provided to the contestants shortly before launch to avoid cheating/tampering/etc.

 

[CycloWizard]

Originally posted by: Howard
Dilatent, is that synonymous with non-Newtonian?

Dilatant is one form of non-Newtonian behavior in which the viscosity of the liquid increases as shear rate increases. These are also called "shear-thickening" fluids. Basically, the faster you shake it, the more viscous it becomes.

 

[TStep]

Pizza: ahh, I see. As a youth, never participated in a contest like this so I have no idea on the rules of the event. One can always pre-build the foam capsule, carving out access to an egg pocket and cap. A teardrop shape, weighted at the bottom would help to get it to fall and land as anticipated. Maybe jello surrounding the egg in the egg pocket would help. Glue the foam cap back on with fast acting glue.

Actually, I would have to believe an egg in mushed up, premade jello, placed in a large freezer baggie, placed in a large bag of foam peanuts would work as well.

 

[eLiu]

i read the title and thought of the physics oplympiad...haha oops

But yeah these kinds of events are great fun. Though not listed, my personal favorite is bridge-building. Or if you're time limited, just have'em make a single 'truss' and put weight on that.

For the eggs...I never got to try this, but what if you put that stuff from the Dr. Suess book around the egg? The "liquid" that turns solid as soon as you apply force? I think you make it with corn starch and water. What that called?

Though imo the best part is when the stuff breaks, not when it works

edit: well it seems that you guys answered my question before I asked it...

 

[MageXX9]

I haven't read most of the responses but here's my thoughts:

Build a vehicle which is powered only by a standard mouse trap. Car which travels the farthest wins.

Use a gearing system, and big slick tires to transfer the energy.

Build a barge by folding an 8in x 8in piece of foil. Barge that floats the most pennies wins.

This is a simple math equation using the 1st derivative. You want to maximize surface area because the larger the surface area the more weight you can handle.

Build a device which will protect an egg from a 2 story drop. Parachuting not allowed.

Rig the egg to be suspended in a box via rubber bands of some sort. Make box big enough/rubber bands long enough to withstand the fall.

 

[DrPizza]

Originally posted by: eLiu
i read the title and thought of the physics oplympiad...haha oops

But yeah these kinds of events are great fun. Though not listed, my personal favorite is bridge-building. Or if you're time limited, just have'em make a single 'truss' and put weight on that.

For the eggs...I never got to try this, but what if you put that stuff from the Dr. Suess book around the egg? The "liquid" that turns solid as soon as you apply force? I think you make it with corn starch and water. What that called?

Though imo the best part is when the stuff breaks, not when it works

edit: well it seems that you guys answered my question before I asked it...

The "liquid" that turns solid as soon as you apply force - dilatent fluid as mentioned above.
The stuff you're referring to (I believe) made from corn starch and water is commonly called ooblech (or something like that)

 

[AluminumStudios]

I'm not a physics expert, but many, many years ago I won one of those egg drop contests.

I put my egg in a small cardboard box which had multiple drinking straws glued to it sticking out in the directions that the box was mostly likely to in (due to it's balance and shape.)

It landed with it's full force almost straight on a few straws which caused them to split ... but they took the force of the fall and the egg was OK

I don't know if it was a good approach or just luck, but I thought I'd share.

 

[CruZan]

I myself won the mousetrap event when I was in the 9th grade. I used legos with the little lego axles on i larger lego thin base. I use the biggest vinyl records for the back and the front wheels. I tied the string to the mousetrap lever and connected it to the back axle...It took off real slow but went the farthest. Legos are very light weight and records provided the least amount of friction along with being very light weight considering the circumference...Once it got to the end of the string it came off the axcel it it just kept rolling (almost 100 feet total)

 

egg part was easy for me in 7th grade. I took a 4 inch by 4 inch box, stuffed toilet paper on the inside, put the egg in, put more toilet paper in...closed the box, wrapped that in more toilet paper and taped it up. Egg didnt break...it worked and was simple.

 

[rgwalt]

For the mouse trap propulsion, my dad and I used a three part "gearing" system when we built a car for Science Olympiad. We had a long piece of flexible rod attached to the mouse trap itself, and a string on the end that we would wrap around flywheels on the back axle. We would start the car going using a large wheel. This would provide an initial boost of speed. Most of the pulling power would come off the small wheel, which would fire second. The medium wheel would fire last to give a final impulse as the pull string released. The bigger the wheel, the fast the car will move, but you will lose pull time.

As for the barge, experimentation would probably work best here. Get a roll of tin foil, some lose change, and start cutting up squares and trying different designs in your bathtub or kitchen sink.

There isn't enough info on the egg drop to allow me to make any kind of suggestions. Are there limitations on the materials used? Is there some sort of tie-breaker? Is weight a factor?

R

 

[jagec]

Originally posted by: rgwalt
For the mouse trap propulsion, my dad and I used a three part "gearing" system when we built a car for Science Olympiad. We had a long piece of flexible rod attached to the mouse trap itself, and a string on the end that we would wrap around flywheels on the back axle. We would start the car going using a large wheel. This would provide an initial boost of speed. Most of the pulling power would come off the small wheel, which would fire second. The medium wheel would fire last to give a final impulse as the pull string released. The bigger the wheel, the fast the car will move, but you will lose pull time.

That's a good idea, and it could be further improved by actually making a "CVT" by carving a tapered shape on the axle and wrapping the string down it like so:

http://img146.echo.cx/img146/774/untitled4wn.gif

Note: I am possibly the world's worst artist.

 

[DrPizza]

I'd think that regardless of the way the mousetrap vehicle was propelled, friction would be the most important factor to overcome. I recall helping my son make his first pinewood derby car many years ago... If you looked at the car, it was *obvious* that he really didn't receive much help from me. However, if you got out the magnifying glass, you'd see that I labored for hours on the 4 nails and wheels to reduce friction to as little as possible (no rough spots, super super smooth nails, tapered nail heads, etc.) That made all the difference it needed.

 

[coomar]

in high school we had cardboard boat compeitions which is kind of the same as the tinfoil one (but with additional complexity due to scale, getting into a boat, crossing a pool, using water-soluble contact cement and the boat starting to fall apart after an hour), to maximize weight carried you have to maximize water displaced (archimedes principle), fold it into a box (without a top), there are structural differences between cardboard and tinfoil though, it would seem to be a lot less of challenge with tinfoil

the egg challege in dependent on the constraints of materials

 

[sao123]

The constrains from the competition are as follows...
1)The mouse trap must be a part of the vehicle... It must be carried with whatever vehicle it propels, or it must propel itself. it must also be the sole source of energy within the system. IE cant use it to light a match which lights a rocket engine and propels the car.

2)Everyone recieves tin foil of the same size & type (no heavy duty, etc), no other external materials can be used as a sealant, floatation, etc. everyone uses the same pennies and water.

3)No constraints on material usage. Object must fall within the accelleration due to gravity. No slowing mechanism or parachutesd. Everyone is presented with egg at beginning of event to place in their device. the egg may not be modified and must be fully retrievable from device after impact.