1st place Mousetrap Car Ideas- using SCIENCE

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Check out Al's website if you want stuff to build your own: https://www.docfizzix.com/
10 quick, practical build tips: https://www.dropbox.com/s/x35qfah75x4gvse/10 Raceday tips.pdf?dl=0
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Summary: To understand how mousetrap cars work you first need to understand the concept of mechanical advantage. There are 4 principles to win with a long distance car:
And 4 principles for winning with a speed car:
Finally, we visit the Science Olympiad to see these principles in action

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Tags:  bridge  nasa  physics  race  science  tricks  1st  place  mousetrap  car  ideas-  using  science 

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Category: Technology
Caption: This is a mousetrap car they're coming. for competitions in high school physics . classes just like the egg drop challenge . or building toothpick bridges the goal. is to build a car that travels the . furthest or goes the fastest but in . either case the only power divided to . move the car is from a single mousetrap . so today i'm going to show you how to . win first place by building some cars . with the world-record holder then we're . gonna go to the west coast championships . to see all these principles in action . and wait don't leave i know that 99. 7% . of you have never nor will ever make one . of these but i will break down in simple . terms how i know this car will go twice . as far as this one and then i'll prove . it and the little discuss why you see . these dvd wheels so often but do they . work and why do some winning cars have . wheels that look like this but before we . fly all the way out the texas to meet . the world record holder i need to lay . the foundation for the one overarching . fundamental physics principle behind the. mousetrap car. it's called mechanical advantage and to. do that i'm gonna need my niece and . nephews imma bet you guys i could lift . my car off the ground using just my . pinkies if i can't do it you have this . kris benjamin but if i can you guys have . to buy me ice cream i am using my pinky . that's what i'm. [music]. this is really good you guys thank you . if you're willing to move a greater . distance you're able to reduce the . amount of force and by a proportional . amount i can't lift 500 pounds worth of . car one time but i could lift 10 pounds . 50 times a mechanical advantage is the . ratio of the output force over the input . force so in this case it's 50 that means . my hand had to travel 50 times further . than just lifting the car in one shot . but the weight was 50 times less so it . was totally worth it this principle of . mechanical advantage is everywhere let's . take a look at a few examples if i have . 4 pulleys that means i have to pull the . rope down 4 times further than the . dumbbell goes up but in exchange . it feels four times lighter so this has . a mechanical advantage of 4 for the ramp . you look at the ratio of the length to . the height your mechanical advantage . therefore is 2 point 2 that means i have . to travel a little further but the brick . should feel 2. 2 times lighter pulling up. the ramp versus just pulling the brick . straight up and sure enough if you . measure each with a scale this is . exactly what you see if you think about . it a screw is just a ramp wrapped around . a nail so here you look at this has . traveled around the thread and divided. by the space in between the threads to . get a mechanical advantage of 9 and as . you know if you really want to multiply. your force use a ratchet wrench now that . is since your hand travels for one full. rotation is 300 times longer than the . distance the screw moves vertically . between one thread the total mechanical . advantage is 300 it's like a really long . short ramp so if this scale reads 6 . pounds the actual clamping force would. be 300 times more or nearly a ton and . with wheels and axles it's the same . story since this wheel diameter is twice . what this one is as you could probably . guess by now this way weighs twice as . much so now we're balanced with a . mechanical advantage of 2 and you'll . also notice if i move this the lesser . weight travels twice as far and finally. we have levers which is where we started . with my niece and nephews here if you . compare the ratio of the distances from . the pivot point we have a mechanical . advantage of 4 which of course means i . have to move this end. four times further but it's super easy . because it's 1/4 the weight on this side . and in all of these examples which you . see everywhere around us you trade lower . force for more distance traveling this . is how humans built amazing things . before all these fancy machines with . engines came around human muscles are . totally strong enough as long as you're . willing to spend a little more distance . to do the task and so this principle . mechanical advantage is at play over and . over again with the mousetrap cars only . in reverse it works both ways in other . words i don't want the full force of the . spring acting over this tiny distance to . act directly on the wheels or they would . spin out that would be a very . inefficient transfer of energy from the . spring so we use mechanical advantage . and make the main lever arm 15 times . longer than the spring lever arm and in . the wheel diameter is 24 times bigger . than the wheel axle so then if we . multiply them our total mechanical . advantage is 1 over 360 that means the . force is 360 times less right here on. the output at the wheels to the floor . versus right here on the input on the . spring it also means will travel 360 . times further than the distance this . spring arm rotates all right so that's . enough of a foundation for now let's go . to texas and meet up with my buddy al to . build some racecars . um eh not only is he the mousetrap car . world record holder but he also kind of . started the whole thing and he was texas . high school physics teacher of the year . and since my dream job is to one day . switch from working as an engineer in . the private sector to go teach high . school physics somewhere . i made him show me all his cool demos i . came up with this idea back in 1991 and . since that time i have literally built . thousands and thousands of mousetrap. cars myself i've seen every possible . engineering design you could ever come . up with there's lots of different . variations for rules for a mousetrap car . race let's talk about how to build the . best long-distance car first for our . testing we started with three identical . cars the only difference was the length . of the lever arm so one was short one . was medium and one was long and i've. calculated each of their mechanical . advantages which you can see written . here given what we know about mechanical . advantage what do you think is about to. happen as you might have guessed the . short lever arm car takes a strong early . lead this makes sense because it has the . largest mechanical advantage therefore. the highest force where the wheels and . ground meet the downside is that it's a . short-lived burst and the medium and . long lever arm cars pass it once it's. quickly used up all its energy in the . end this is how far they each traveled . with the longest lever arm car going the . slowest but making it all the way to 30 . feet this brings up the first principle . for the long distance car to win you won . the smallest possible force over the. longest possible distance in other words . the smallest fraction for mechanical . advantage possible you want your car to . be barely creeping forward to waste as . little energy as possible you think as a . total energy of the spring as this . amount of water in this cup and then . this cup represents the amount of energy . that's passed on to your car to move it . forward if you just quickly dump it all . the energy a ton spills and splashes out. this will be due to losses from extra . heat generated or even drag force from. the wind which is proportional to your . velocity squared but if you do it slowly . and more controlled much more energy . goes to actually moving your car forward . the next thing we tested was adding . graphite to the axles on all three of . the cars and then we we erased them . this made a huge difference and now they . went this far again . the longest lever arm car one because it. was the slowest but this shows the . importance of dealing with friction it's . definitely your biggest enemy with these . cars and the friction comes from two . spots you have the rolling friction . between the wheels and the ground and . then the biggie is between their axles . and the car body this is why we put the . lubricating graphite powder there to . take our testing a step further we took . the long lever arm car and added ball . bearings and place at the graphite and . that set a new record for us at 50 feet . so if you only have one hour to make . your car and you want to have a good . showing you can use a long lever arm . like this in conjunction with the cd . wheels to give you a mechanical . advantage of about one over 360 and then . use ball bearings at the axles or just . apply some graphite and you're gonna do . pretty well next we figured if long . lever arms make it travel slower and. therefore further we should do a super . long lever arm but it only made it to . here which was worse than even the short . lever arm car the problem was that it . didn't coast very well because we had to . make it really big which means it's more . heavy which means more friction you know . this already intuitively because it's . harder to push a heavy object on a table . than a light object because there's more . friction resisting you so principle . three is to make it lightweight i love . this example though because it shows you . need to balance these principles if you . take any one of them too far then . another principle will creep in and. start penalizing you . it's an optimization problem and that's . what makes the mousetrap reasoner's such . a great project that's also why testing . is so important so tweaking and testing . different things like allen i did is . critical for honing in on the sweet spot . for your specific design next we tried . this big wheel design which is a popular. approach the strategy here is the wheel . is 56 times larger than the wheel axle . so when you combine it with the lever . arm you get a built in mechanical . advantage of one over 840 and that's the . equivalent of. her arm that's two and a half feet long . but without needing the big heavy car . that seems like a good deal and as such . it was our best car yet . and ma

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