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[-] cumnan@lemmy.world 166 points 8 months ago

If the vehicle maintained a constant velocity and there was no air resistance, the diver would enter the pool.

In the real world, air resistance would cause the diver's velocity to decrease relative to the vehicle and thus the second panel is a probable outcome.

[-] Hugin@lemmy.world 97 points 8 months ago

I don't think you can assume constant velocity. 16 forward movement lines on the top vs 13 on the bottom so it's moving at 81.25% speed in the bottom compared to the top.

[-] pooberbee@lemmy.ml 48 points 8 months ago

Pretty sure speed lines increase logarithmically with speed, not linearly.

[-] sawdustprophet@midwest.social 14 points 8 months ago

Pretty sure speed lines increase logarithmically with speed, not linearly.

Does this account for the presence of speed holes?

[-] A_Very_Big_Fan@lemmy.world 10 points 8 months ago

Pretty sure speed lines increase logarithmically with speed, not linearly.

Does this account for the presence of speed holes?

You don't have to quote the entire reply for them to know what you're responding to lmao

[-] Steve@startrek.website 8 points 8 months ago

African or European style?

[-] SkyNTP@lemmy.ml 12 points 8 months ago

Wow. I am truly impressed.

[-] andrew@lemmy.stuart.fun 4 points 8 months ago

You can though, unless the water in the pool has no momentum. It would not be flat if the vehicle was accelerating enough to move that far in a 2-3 second dive.

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[-] ryathal@sh.itjust.works 19 points 8 months ago

It would depend on the speed, and any speed a person could actually stand an jump from is likely slow enough they still land in the pool.

[-] Limonene@lemmy.world 13 points 8 months ago

The diver would feel the same wind while in the air as while standing on that elevated diving board. He would recognize the strong 70Mph wind, and jump forward to counteract it.

[-] snooggums@kbin.social 25 points 8 months ago

He wouldn't be casually standing on the board at 70 mph either, so any wind strong enough to push him off the back would make it really hard to stand and dive in the first place.

[-] GBU_28@lemm.ee 3 points 8 months ago

He is exerting force on the diving board to stay in position. Gripping with his feet, and leaning.

Sure when you jump you.would.natutslly try to compensate, but I don't think you'd land where you hope, it would be very hard to gauge the needed force, or even produce it.

[-] Assman@sh.itjust.works 10 points 8 months ago

Got it, do not attempt while inside the atmosphere

[-] ArgentRaven@lemmy.world 9 points 8 months ago

You wouldn't drive an RV with a pool on the top very fast at all. It'd be a dangerous tipping hazard on any turn, and sudden acceleration or deceleration would cause the water to spill out.

Assuming they're not going 80, and more likely not even 55, the diver would have more than enough force to jump forward into the water.

[-] Treczoks@lemmy.world 7 points 8 months ago

I doubt they are fast enough to blow him that far off. My bet would be that he falls flat on the middle of that board.

[-] Ulvain@sh.itjust.works 9 points 8 months ago

Idk, have you ever put your hand out the window of the car, going 60k/h? That's just 50 sq.cm of air resistance... Imagine a whole body's worth

[-] dangblingus@lemmy.dbzer0.com 2 points 8 months ago

50cm^2? That's a baby hand.

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[-] SeattleRain@lemmy.world 1 points 4 months ago

Yeah, air resistance and friction from the road are the primary reason why the car's engine has to keep running.

[-] Caboose12000@lemmy.world 102 points 8 months ago

the woman's hair is blowing the wrong way

[-] UlfKirsten@feddit.de 27 points 8 months ago

I think it’s supposed to be a fish with a full body mask

[-] The_Picard_Maneuver@startrek.website 16 points 8 months ago

Wait, maybe they're reversing then? This adds new questions.

[-] xia@lemmy.sdf.org 3 points 8 months ago

Maybe the bottom pic comes first chronologically?

[-] olafurp@lemmy.world 7 points 8 months ago

It's tied in a bun I think

[-] HeyThisIsntTheYMCA@lemmy.world 5 points 8 months ago

That's not hair

[-] FMT99@lemmy.world 45 points 8 months ago

I can't answer this without at least one spherical cow in the frame of reference.

[-] emergencyfood@sh.itjust.works 12 points 8 months ago

I'll allow it on condition it has negligible mass.

[-] Deconceptualist@lemm.ee 6 points 8 months ago

Ok but what are its charge and spin values?

[-] noughtnaut@lemmy.world 41 points 8 months ago* (last edited 8 months ago)

This is related to the "airplane on a treadmill" myth (go watch).

Preservation of momentum

I wanna say it's incorrect, but really I'll say it's exaggerated. The man on the diving board is going to continue moving forwards just like the rest of the gear, he's not going to suddenly stop on relation to the road surface. However, he is going to be affected by wind resistance (which scales ~~exponentially~~ quadratically with speed) so he will need to make a good forward leap in order to not fall behind because of that. If he doesn't, he would be effective jumping backwards - but not as far as depicted (unless the car is travelling really, really fast).

If the pool (and indeed, the man) were encased within an envelope to protect from that wind resistance, he would be entirely unaffected. So there.

[-] Bridger@sh.itjust.works 18 points 8 months ago

It's not just how fast the car is going. How high the diver jumps (how long he's in the air) also factors in.

[-] tiredofsametab@kbin.social 3 points 8 months ago

Unless the driver tosses it in neutral, the engine is also still doing work even if keeping the car's speed constant whereas when the diver jumps, I think he stops being a part of that system he will slow down compared to the van, right? How much this affects the landing of the jump depends upon speed, wind speed, etc.

[-] iAvicenna@lemmy.world 30 points 8 months ago

If the car is accelerating quite jerkly then this should be possible

[-] Ephera@lemmy.ml 24 points 8 months ago

Or going fast enough that air friction would decelerate the guy this much.

[-] kogasa@programming.dev 7 points 8 months ago

He would need to be gripping extremely hard with his feet and somehow keeping his body rigid in the first panel

[-] Ephera@lemmy.ml 3 points 8 months ago

I'm imagining him having taken a bit of a run-up and this is the moment when he's momentarily at the same speed as the car. Obviously, it is still somewhat of a stretch...

[-] HiddenLychee@lemmy.world 9 points 8 months ago

Fun fact for anyone reading this, the time derivative of position is velocity, the time derivative of that is acceleration, and the time derivative of that is jerk. Then after that comes snap-->crackle-->pop

[-] gasgiant@lemmy.ml 25 points 8 months ago

The real answer is it depends how the diver is exerting force as he stands there and what force he has to overcome to jump forwards.

If he's using all his driving force through his legs just to stand there then when he jumps up he will go backwards.

If he was casually standing there easily overcoming the push of the air already then he can jump into the pool just as normal.

It's the same as standing next to a swimming pool with different wind speeds. Small breeze = jump in ok. Hurricane = blown backwards.

That's assuming he wasn't trying to jump off the back of the vehicle.....

[-] rosymind@leminal.space 6 points 8 months ago

Also assuming the van doesn't suddenly, greatly, accelerate

[-] april@lemmy.world 12 points 8 months ago

It works if the wind is really strong, but everyone knows physicists can only handle frictionless vacuums

[-] DebatableRaccoon@lemmy.ca 9 points 8 months ago* (last edited 8 months ago)

It's impossible to say how far back the diver would end up relative to the vehicle but from the moment he lost contact with the diving board he'd be subject to deceleration from wind resistance while the vehicle would still be going at whatever speed it already was so seems decently accurate. (Just wait for the Lemmy physics professors to tell me I'm wrong)

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[-] Fedizen@lemmy.world 5 points 8 months ago* (last edited 8 months ago)

car would have to be accelerating or.. moving fast enough that wind resistance was significant (the air is probably not moving with the car)

[-] open_world@lemmy.world 4 points 8 months ago* (last edited 8 months ago)

If the vehicle is moving at a constant speed, then the guy should be moving at the same speed in the direction of the vehicle during the jump since they're in the same reference frame, so there's no reason why he would suddenly lag behind and jump onto the ground.

Edit: Damn physics classes conditioned me into always assuming air resistance is 0!

[-] glimse@lemmy.world 9 points 8 months ago

The vehicle overcomes air resistance with an engine and maintains its speed. The jumper has no engine and will be affected by air resistance

Like the other commenter said, the comic is exaggerated but true

[-] ricecake@sh.itjust.works 3 points 8 months ago

Unless the jumper is farting really hard.

Checkmate.

[-] Peppycito@sh.itjust.works 5 points 8 months ago

A head wind would be one reason.

[-] yesman@lemmy.world 3 points 8 months ago

You guys are all confused. The real question is will the diver be injured more by falling on the pavement than diving into such a shallow pool?

If the pool is deep enough to accommodate the diver, then there is no way that car could tow the RV nor any way for those tires to support it, thus the velocity is zero.

[-] doctorcrimson@lemmy.today 2 points 8 months ago* (last edited 8 months ago)

The real question is whether his momentum overcomes the wind resistance. Probably not.

[-] genie@lemmy.world 2 points 8 months ago

The real question is where do you sleep in that camper

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this post was submitted on 12 Jan 2024
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