Place Your Bet: How far will a dumbbell squirt soap?

This is the first episode of a series I'm calling Engineered Bets, which tests theory vs. reality and it's your job to determine what will actually happen relative to the calculated line. I'm going to experiment with more and less complex topics to see what people enjoy the most, so I'd love your feedback about the topics, pacing or anything else. Thanks for watching!
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[@JaDroppingScience]

New episode of 2 Truths & Trash should be out on the 1st! Any feedback about this new series would be greatly appreciated. Thanks for watching!

[@Womcataclysm]

It was fun but most people won't want to see all the calculations, you should add chapters in the video so people can skip to different parts, and also, maybe add a quick recap/TL:DW of the math before you get to the reveal, maybe even just a "pause here" so people can read at their own pace, not sure. Still, felt a bit long for just one bet, but I did watch it and I liked it

[@Tickingclock4]

I think this was better

[@flilium2086]

This Engineered bets- series would be so awesome.

[@transrightsbaybee]

this was so fun !! i loved how whimsical the scenario is [:

[@megauberduber]

As a mechanical engineer this fucks, please make more

[@ZevVeli]

I said under. I think that the reason it went over is that when the dumbbell hit the dispenser and broke it, it angled the trajectory upwards thereby increasing the amount of time the soap was in the air.

[@AsmeowdeuZz]

I would say the soap droed nearly indicate they have less initial momentum energy, and some of these energy convert to the furthest part of the soap

[@iarmycombo5659]

I said under because some would certainly hit below, but i said if only looking for furthest its for sure over. I assume now in hindsight that the over bit is because the soap doesnt act as 1 block of matter as the math assumes, it clings to the walls, thus creating turbulance, basically creating a smaller divider for the tube and launching a small amount of soap that travels in the smaller "tube" further because of it technically having more pressure because same force less volume as the volume is eaten up by the soap that is stuck to the walls by the friction. Also it could be affected by the fact that its probably a designed 90 degree angle in the piping but the soap stuck to the walls of the pipe smooth out the corners and create a f(x)=ln(x) shape for the unstuck moving soap in the tube/pipe, that could allow the soap to still have a small but existing vertical component that allows for more airtime.

[@1islam1]

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[@beetcat6137]

@@1islam1 yes im sure that contributed to the soap going further

[@nope.0.]

I guessed under, with the dispenser being knocked over forwards, decreasing air time.

[@tulaibhussain5013]

From the beginning I was convinced the dumbbell would shatter the jar and no soap would exit at all. I thought this whole video was a build up to point out no matter how theoretical you think, reality will always differ from calculations. When you said "Think how reality vary will this simple model. Now lets see what actually happened" I was so convinced I didn't even guess.

[@JaDroppingScience]

Haha yeah I thought about how that could happen. If it did (or does for future episodes), 0 feet would still be considered under.

[@anj000]

@@JaDroppingScience you need to make a short out of it, but stage it so that the soap dispenser shatters. It will be hilarious!

[@calabrais]

Reminds me of a software engineering joke. A quality tester enters a bar and orders a beer, 100 beers, 0 beers, -1 beers and everything is fine. A customer enters the bar and asks to use the bathroom and the bar explodes.

[@TYsdrawkcaB]

@@calabrais IT TOOK A SECOND BUT THAT’S SO FUCKING GOOD HOLY SHIT

[@Cp12321]

​@TYsdrawkcaB can you please explain it

[@FatBoiFishy10]

very important information

[@user-gq7gi5hv4u]

Fr

[@wareqo9768]

man where was this kind of video when i was taking physics, it makes it so much easier to understand than form a book

[@blairhoughton7918]

I remember the chain reaction demo film where they threw a ping pong ball into a room full of ping pong balls on mousetraps. And that was old when we got it. So this kind of science education has always been around.

[@wareqo9768]

@@blairhoughton7918 well it's more about how engaging the content is than the content not being around. It's not like I was taking physics ages ago, it was more about not finding engaging explanations.

[@visillac]

Pretty wild how it landed right on the 7.9 mark. My guess is it went a bit forward after splattering then coming to a full stop

[@sammiecakie8973]

Ok but why on earth are we using feet??? Like that must be a crime against science to not use SI units

[@Jack22024]

Feet are freedom units

[@jwalster9412]

American Freedom is a ​sham. @@Jack22024

[@ezriha]

Size of 1.5 washing machines.

[@enderyu]

My guess for the reason it could have overshot: The calculation (1:50) of the velocity on the nozzle is the minimum velocity necessary so the fluid does not get compressed. However, since the fluid was in rest and suddenly forced to move it creates a slight over-pressure that makes the initial burst of soap have a slightly higher velocity than expected

[@lukedieleman6676]

My initial 1 second reaction was over, but after watching the calculations I changed my mind to under. My guess as to why the soap went a bit further than the line is likely due to the assumption that the flow of soap will fill the entire area of the nozzle. I would be willing to bet that some portion of the nozzle choked a small portion of the flow more than the exit itself did, which would accelerate it more, also the nozzle was slightly angled upwards, which could have allowed some part of the flow to exit at a slightly higher angle. I'm also fairly sure these calculations are ignoring the effects of viscosity as well as boundary friction, which would help to explain why the bulk of the soap only went 3 or 4 feet.

[@sams.8188]

this went way over my head but was still fun. good series

[@IOSARBX]

JaDropping Science, This is amazing! I subscribed right away!

[@nikhiljayansingla5323]

This is literally Ja "Dropping" Science.... 😂😂

[@rqlk]

Now you just need a perfect vacuum and a perfectly efficient and indestructible soap dispenser.

[@2thecartoonsimp1]

"I mean, what is air resistence anyways?" -Hamiltonian mechanics

[@mxm650]

My initial thought when I saw the setup was, "It might be a good idea to prop up the soap dispenser so it doesn't get knocked over." I loved this! It brought back fond memories of engineering school. Do more, please!

[@mythicul]

I love gambling

[@Snowflame47]

this video is actually super sick. I just finished my junior year as mechanical engineering student and this video reminded me how much I’ve actually learned and how I can apply that knowledge. good stuff, dude.

[@OfficalMcM]

Please make a series out of this, this is very fun to watch

[@matt22953]

Thank you for this. Hope are making videos like this.

[@jamesmarker3956]

If you look at the end of the trail of the soap, it’s behind the 7.9ft estimate. My guess for why it went over is that when it hit the ground, because our x component of velocity was so large, the inertia of the soap allowed a gloop of it to keep moving a couple of inches.

[@toron4]

I loved the little nod to 3Blue1Brown, very fun.

[@divy1211]

I guessed under: as a kid, I've tried to hit the soap dispenser just to see how far it could go and I generally found that when you do that, you get yelled at by your mom. the yelling aside, I always found it hard to make it go far with an impulse, and I actually managed to get it to go further if I just pressed the thing really hard instead of hitting it. So I figured the majority of the soap wouldn't even go half way which was about right. I forgot to account for the little splats though, which made the result over XD I believe the reason the majority of it doesn't go as far is because of viscosity and friction with the walls, and the fact that soap dispensers are generally not water tight, so there'd be energy lost to compression and air

[@2thecartoonsimp1]

Nostalgia>Physics

[@endunry2]

Saw your ig reel, hadnt known you before but starting binge watching your yt content now

[@edelledezma9872]

excellent phisics demostration, loved the video

[@peterking6334]

Love your videos

[@LocalPlagueDoc]

Congratulations! You made physics fun and engaging! PLEASE continue making videos like these, you struck a goldmine with this!

[@JaDroppingScience]

Thanks so much!

[@TheBluePhoenix008]

This is amazing!

[@MJBsor]

My guess for why it went further, is due to the fact that the nozzle is moving down, that the soap slows down the moment it leaves the nozzle and the soap exiting behind it is at a constant velocity, so the soap exiting pushed the soap that exited upwards at a slightly higher angle.

[@rorydakin8048]

I chose over 7.9 feet because thick fluids like soap have a "sheer force" which would essentially reduce the exit diameter much more than just the physical restraints of the nozzle, basically the thick fluid sticks to the wall and moves slower, but the fluid itself does not stick to itself the same way. This causes an overall reduction in exit diameter, and thus an overall higher exit velocity. Note that this will only occur if the sheer force is lower than the input force, pressing the nozzle with 50lbs of sharp and fast force (0.1 seconds) vs the same overall force slowly over 10 seconds will yield completely different results

[@Yezpahr]

I thought over, but for the wrong reasons. When you said "and that's how the 7.9 feet mark was set" my mind started racing and the tinier hole after the plug may impede it more than I anticipated. I presumed all those holes in the dispenser were the same size but you showed they weren't. I did expect the dispenser to just break outright and a good result would require it to be primed properly and have no dried up clog of soap in the last hole. (sometimes a small layer can gel up or crystallize even)

[@XanquaTheWatcher]

I said under! My guess was that because of how heavy the dumbell was, it would push it down really fast, goving it more distance than expected. Since "expected" was the line, past it made the most amount of sense to me.

[@MoonGlow22]

But we calculated thinking the soap wont spread and cummulate at one place And if we take average distance of the shooten soap, its deffinetly under

[@Vaaaaadim]

I guessed under, just because friction wasn't accounted for. A qualm I have with this is that the experiment was only conducted once. One of the comments noted the possibility that as the dumbbell hit the dispenser it may have angled the trajectory upwards. If the experiment was repeated it might have played out differently where the trajectory was angled further up or down.

[@EDoyl]

This is really great 👍

[@edwardsmoliak109]

This was a good concept.

[@blairhoughton7918]

I said under, thinking the nozzle would slightly depress before any soap came out, lowering y0 thus shortening xf. The over result is interesting. My best guesses are that the dumbell tilted the nozzle back and up a bit, giving a higher launch angle; or, liquid soap is non-Newtonian and that contributed to a more energetic, springier ejection from the nozzle, and also to the less springy compression inside that broke the device.

[@Meowy-go8pd]

Got it right 😊

[@MarkCupLee]

Due to the transient nature of this interaction, it's better to tackle this problem in terms of energy. Since only small amount of the soap will be launched. If all of the energy from the bell is transfered into the soap, it will be launched with a ridiculously high speed. Even taking into account the heavy loss of energy, the unknown amount of soap should be launched quite far still. That's my chain of thought into this problem as a mechanical engineer.

[@suishregmi9911]

I thought it would go over and I think my reasoning is correct, please correct me if I am wrong. The 7.9 value we calculated was the point where the soap hits the ground initially, as we see accounting for air resistance it is appropriately 7.8 or somewhere around that. But the horizontal velocity doesn't suddenly goes to zero it encounters certain friction and travels certain more distance before stopping.

[@borntoclimb7116]

This is the most interesting soap and drop Video.

[@gullybonesart4670]

I guessed over because I’ve launched soap like that before. I think the speed at which the piston compresses contributes the most, from personal experience.

[@anthonyzeedyk406]

It probably has something to do with the change in the cross-sectional area of the pump apertures. Those are difficult to measure and have a large impact on the final velocity of the soap.

[@autodidact7127]

This was a lot of fun

[@jeffguo7371]

The center of mass of the dumbbell is higher, so you might have underestimated potential energy if you just take the distance between the bottom of the dumbbell and the top of the dispenser as the height. Also, this is a transient flow question, the continuity equation assumes the soap has constant velocity, which is not the case here.

[@Practicing_HVACR]

Great video! Loved the thorough explanation. I’m most suspicious of the angle. 4 degrees seems like it was rounded and I would imagine a small difference can easily change the distance slightly.

[@gEtar87]

New drinking game- playlist this channel and every time someone gets it wrong, they drink.

[@atesemireltutar6661]

We were assuming that the soap would stay intact when we were calculated the 7.9 feet distance. But as we can see soap broke apart in the air and therefore momentum calculations do not work anymore. The soap could have broken up in such a way where no soap particle gained momentum in the right way and it could have undershoot. I don't believe it is DETERMINED that it would overshoot.

[@Tletna]

I said under because I believed the mass and spring force of the soap dispenser would resist the impact of the weight (also no fluid is 100% non-compressible, eg water is said to not compress but it still does some with enough pressure). I did not realize that the container would break and that the fluid would then shoot out harder than expected and I also believe when some of the fluid started to separate from the rest that might explain why most of it was below the 7.9 feet but a little bit broke off to go beyond the 7.9 feet. It would make sense that the part that broke off had less mass and would increase in velocity after breaking away. However, this is just a theory on why it happened. I still did not expect this result and cannot fully explain it.

[@EDoyl]

Soap behind pushed on soap ahead, a bit like that demonstration where you stack bouncy balls on top of each other and drop them all. If you recorded in super slow motion you might even see smaller droplets spraying out that went further still.

[@moonystar6291]

I thought under, on the assumption that the dumbbell probably wouldn't fall perfectly and so therefore wouldn't depress the plunger properly, adding in too much instability for it to reach it's potential.

[@Jack22024]

I said over because the initial force of the dumbbell compressed the spring with enough force to make the soap shoot out like a rocket

[@devl8565]

This is the type of question that helped me get extra credit for my physics classes 😂

[@tf9956]

I said over. My guess is that it was angled slightly higher from horizontal at impact. My other guess was maybe a calculation mistake? I graphed equation using the same numbers, and I have time equal to 0.057 seconds, which would lead to ~8.3 feet. It was calculated using my ti-83 calculator.

[@Draconic404]

having hit a soap dispenser really hard before made the choice easy, thgose things are powerful!

[@2thecartoonsimp1]

I think the video is amazing, but if you will make another video of this style, I recommend to put more accruate date as I've tried to do the trajectory before watching the results and I got 8.7ft rather than 7.9ft due to the data being to approximated. Would appreciate if you did that, and great video.

[@user-uo1yn4se8r]

I guessed down because the spring decelerates the dispenser when the dumbell hits it I think the main factor that caused the result to be higher than estimated is that the soap continues to move forward and smear on the floor after it hits the floor

[@Stooge2]

7.4 feet Dang

[@ShawnF6FHellcat]

I graduated high school as the top of my class for math and science, and this made me feel invalidated... It's like if you play an instrument, then you see someone quite a bit younger than you play the same instrument far better than you could ever dream to... Why is it that I feel this way???

[@domi-no1826]

I watched the short first and picked over, if i saw this i would’ve gotten it wrong!

[@bachira0__]

That was all science i knew

[@Azur638]

I was thinking that sice things like friction, momentum, and liquid compression exist, there would be more pressure in the soup directly before launce, resulting in slightly longer shot.

[@Asteroid_Jam]

I think it went over as you found the potential energy from the edge of the bottom of the dumbbell not at the center of mass of the dumbbell.

[@devavratkhandekar4020]

I think the few drops which landed before the 7.9(theoretical mark) lost kinetic energy and the dropes that when to 8.1 ft gained proportional ke lost by prev drops. The ratio of drops which landed after 7.9 ft to before 7.9 ft should support this theory. Due to conventional energy losses, the drops should actually land before the theoretical maximum of 7.9 ft.

[@Temporary_yesyes]

guessing under as the dumbell moves down the end of the dispenser so if the flow rate is the same as the speed going down it'll only go forwards a maximum of 45º

[@helper_bot]

i just guessed it was under because i didnt really think the momentum would transfer over if the suction transfer function is just as bad as the dispenser in my house

[@octocatpug2327]

I thought the viscosity would have had more of a effect, though it seems with that pressure it doesn't quite matter

[@BJ-GAMING.NR.1]

The calculation you have made is very theoretical, you also have to take into account the air resistance and the viscosity of the soap and then it must be the largest amount you have to count on and not whether there are small drops here and there that get further than the total largest amount. It's just like when a person throws a discus, that's also where the first impact is, it also counts even if it slides further.

[@merukit]

I think the assumption at 1:55 is inaccurate, in such a collision it might be that the head of the soap dispenser is accelerated to move downwards faster than the speed of the dumbell, which might contribute to it shooting over the line

[@Alex_49_YT]

I thought due to energy loss through the spring and some kinetic energy loss off the soap through the valve it would go under, but I think the dispenser was hit so it pointed up when launching the soap. Edit: Watching it back, the dispenser wasn’t pointing up I think, but maybe because it broke something about the pressure in the valve changed?

[@blaster2586]

I was thinking that the reason some soap went further is conservation of momentum. Since it’s not a line, it’s a big projectile breaking into others. Original momentum=final momentum. So if some didn’t go as far, the rest would have to travel further to compensate (this is from a basic understanding I’m no physicist). I said under though so consider my Jaw dropped!

[@theopoldthegamer4284]

I'm expecting the soap dispenser to be destroyed, causing the soap to launch WAY under the expected distance

[@SupernovaSpence]

We also forgot about skips… I’d like to see the video over the whole distance :)

[@TheBeeMaster9721]

This much work just to calculate how far soap will go… Very detailed though!

[@HaHAjax]

at first i thought we were predicting how far the bottle itself was going to launch, not the soap inside

[@kaphity8506]

I predicted under. and if the soap didnt seperate it would be under. The „average“ distance the mass traveled is under. But not everybody in a society of soap is the same, and thats fine with me, it’s called variety (or on this case varience)

[@oh_tassos]

Additionally to what others have said, could it be that as the soap bottle broke potential energy from the spring was released and somehow turned into kinetic energy on the soap?

[@anidynium1106]

ill use this in my day to day life like my math teacher told me

[@rafa_br34]

I also thought it would be under, primarily because the model you used doesn't apply the losses such as friction, no idea why it went over 7.9 tho.

[@lucasbrelivet5238]

I chose under. I think it actually landed under, but didn't stop immediately after hitting the ground.

[@parthhooda3713]

The point when he said: let's assume that dumbbell transfers all momentum I thought in reality it won't so it should be under but for some reason I was wrong.

[@josephbevan1036]

Over, the dumbbell is gonna angle the nozzle up slightly which is gonna increase the distance.

[@lautaromorales2903]

could this be calculed with the kinetic energy of the lanched soap being the same as the potential energy of the dumbell? you only need the mass of soap, the mass of the dumbell and the height

[@KingJellyfishII]

Doing all these calculations in imperial physically hurt me

[@inplfw]

I expected under. I wonder how the properties of the fluid affects this. I have to imagine that on a spectrum from water to honey you'd end up with different distances shot.

[@parthhooda3713]

2:15 bro really included even that 4° or 0.06981317 radians of angle 💀

[@Itsmmkk]

But the average drop what behind the initial line, so technically behind is the right answer right?

[@jacobtaylor8206]

i think the change in angel is the biggest contributor

[@MooImABunny]

It's nice how you went over all the details of the model. absolutely disgusting seeing empirical in mechanics calculations, but nice video

[@LangSphere]

3:33 i'm gonna guess over

[@TheTrueSuper]

But what if you held a hair dryer upside down pointing at an amgle upwards behind it to give it a speed boost as it leaves the pump?

[@aayank7722]

What level of Complexity is the physics involved here? It seems to be around high school level, perhaps first year college?

[@maxwellgao1662]

I thought it would be over because some initial fluid compression might cause it to burst the nozzle faster. Funny video though

[@stevelewnau193]

I said under. Thought maybe the soap would act as a non-Newtonian fluid at very high force and basically resist the dumbbell. 🤷‍♂️

[@ElNerdoLoco]

initial guess: 4.5 feet. Edit: well, went further than I thought. I was just thinking about how much resistance that kind of pump feels like it has to sudden impacts and kind of wondered if soap becomes more viscous under pressure.

[@xd-qi6ry]

Definitely the height of the pump itself

[@jan_Masilijun]

please use si units

[@E-dart]

i think that it was over because the dumbbell still couldave accelerated after making contact with the pump thing

[@kiahplaysroblox4159]

Simply the soap dispenser will just break

[@AS26005]

why didn't you use the metric system?

[@JaDroppingScience]

I'll do both throughout the series. Metric is always nicer but the tape measure I had was in inches so I just kept it lol

[@2OXX]

BECAUSE THIS IS FREEDOM LAND YOU COMMIE

[@nukezillagaming5198]

3 inches like me 😢

[@kenny456100]

I guessed under becuz I assumed the soap solution is non-newtonian and will not eject much when the bell dropped.