totm aug 2023 What funny/interesting thing happened in your life today?

[Sorabh]

1 hour ago, YNM said:

Huh ? Last time I was in one there wasn't much headroom but definitely enough space for turning in the gangway.

Unless some really vile people has turned it into 2-3 configuration.

It was 2-2. He was getting off his seat so that I could get to the window seat. He wasn't really paying attention, so SLAM! And I was talking about the legroom being small.. Its soooo squeezy... Like a minivan drank redbull, and it grew wings..

 

Edited October 15, 2018 by Sorabh

[CatastrophicFailure]

Do they at least give you a free pass or something?

[DarkOwl57]

So we've been tasked with building a catapult in Physics class.

Size limits: 3m x 3m x 2m (LWH)

Cost limits: $20

Timeframe: Oct. 15 - Oct. 29

Projectile: Tennis Ball

Self-doubt: High

Also during Physics: Our class learned how to flick pennies by snapping. I'm taking cover behind my desk as tiny WMDs land all around me. I fear for my life.

Edited October 15, 2018 by DarkOwl57

[TheSaint]

32 minutes ago, tater said:

The tram base is under 600m from my house.

I wish it was more often a ski lift. We have ski runs on the other side, and the tram is at the top of the regular lifts, but it's not open very much, our weather here tends to be pretty variable. An hour north in Santa Fe the ski area stays open, largely due to being a little farther north, and having weather more like Colorado.

Our kids were seriously disappointed with the winter weather last year. There was one snowstorm, an overnight flurry right before Christmas, it only deposited about 1/4" and that was gone by about 9:00 the next morning. And we were in California for it. They literally received more snow in Houston last year than we did.

[qzgy]

On 10/15/2018 at 12:35 PM, DarkOwl57 said:

So we've been tasked with building a catapult in Physics class.

Size limits: 3m x 3m x 2m (LWH)

Cost limits: $20

Timeframe: Oct. 15 - Oct. 29

Projectile: Tennis Ball

Self-doubt: High

Also during Physics: Our class learned how to flick pennies by snapping. I'm taking cover behind my desk as tiny WMDs land all around me. I fear for my life.

Sounds.... Fun!

How far can you stretch catapult? Cause if catapult just means launcher, i would suggest building something like this or maybe some air pressurised canon.

Or you know, giant slingshot.

[razark]

On 10/15/2018 at 11:35 AM, DarkOwl57 said:

Size limits: 3m x 3m x 2m

How firm it this limit?  Is this the starting conditions, the ending conditions, or does this limit encompass the entire operating time?

 

On 10/15/2018 at 11:35 AM, DarkOwl57 said:

Cost limits: $20

It's amazing how cheap materials can be if someone just happens to have them "laying around" in the garage.

I mean, who's to say someone doesn't have a short length of pipe, some wheels, and a bit of lumber in the garage that they're willing to "sell" for $20?

[Mad Rocket Scientist]

On 10/15/2018 at 9:35 AM, DarkOwl57 said:

So we've been tasked with building a catapult in Physics class.

Size limits: 3m x 3m x 2m (LWH)

Cost limits: $20

Timeframe: Oct. 15 - Oct. 29

Projectile: Tennis Ball

Self-doubt: High

Don't doubt yourself. It will be fun!

Also, see if you can get away with using a model rocket engine to add power.

[p1t1o]

The ONLY way, IMO

[DarkOwl57]

12 hours ago, qzgy said:

Sounds.... Fun!

How far can you stretch catapult? Cause if catapult just means launcher, i would suggest building something like this or maybe some air pressurised canon.

Or you know, giant slingshot.

It is a really exciting challenge- I'm just a bit nervous that I'm going to find a way to screw it up. Unfortunately, slingshots, air cannons, or anything that has to do with air pressure or explosives is illegal in the projects- it's pure swinging motion. 

12 hours ago, razark said:

How firm it this limit?  Is this the starting conditions, the ending conditions, or does this limit encompass the entire operating time?

 

It's amazing how cheap materials can be if someone just happens to have them "laying around" in the garage.

I mean, who's to say someone doesn't have a short length of pipe, some wheels, and a bit of lumber in the garage that they're willing to "sell" for $20?

The limits are when the "arm" is fully cocked back, ready to fire. When the arm's firing, it can go as big as we want.

My uncle works at a big place where they build a lot of stuff, and he's got a good bit of wood lying around. I'll probably ask him when he gets back from England this weekend. 

11 hours ago, Mad Rocket Scientist said:

Don't doubt yourself. It will be fun!

Also, see if you can get away with using a model rocket engine to add power.

According to the Juniors, this is an amazing project. 

Unfortunately, can't use rockets, gunpowder, etc. (See the response a couple quotes above)

[cubinator]

I got to talk with retired Shuttle astronaut Curt Brown today! He is very excited for our generation which will get to go to Mars and go to space more frequently, and offered some gold advice for aspiring astronauts. 

• It doesn't matter what you study as long as you do what you love.
• They won't seek you out to become an astronaut, if you want to do it you have to apply - and you might as well.
• If something is worth doing, give it your all.

[0111narwhalz]

9 hours ago, DarkOwl57 said:

It is a really exciting challenge- I'm just a bit nervous that I'm going to find a way to screw it up. Unfortunately, slingshots, air cannons, or anything that has to do with air pressure or explosives is illegal in the projects- it's pure swinging motion. 

Does it have to be swinging, or can you make a ballista out of some old leaf springs?

[DarkOwl57]

14 minutes ago, 0111narwhalz said:

Does it have to be swinging, or can you make a ballista out of some old leaf springs?

Nope

[0111narwhalz]

11 minutes ago, DarkOwl57 said:

Nope

Not sure what you're noping here.

[ProtoJeb21]

Last Friday, my AP Physics teacher was using an old Coyote and Roadrunner cartoon as an example for a kinematics problem, which gave me an idea for something to do that weekend: figure out how freakishly fast Wile E. Coyote is going on his Acme rocket skates. 

Here’s the clip I used:

 

To get results that even mean anything, I needed a way to measure the distance Coyote was traveling. So I decided to use Coyote himself as my ruler for this investigation. Estimating the distance from his head to rump at 0.875 m (between the average length of 0.85 to 0.90 m for a regular coyote) and using pixel measurements, I got his total height of 1.7468 m. Using that, I could find the meter/pixel ratio of the zoomed-out scene showing him and the Roadrunner on that mountainside road and measure the distance Coyote traveled between the final two bushes. This turned out to be 11.4393 meters. Next I had to find the time it took Coyote to travel between those two bushes...which was not easy. I had to slow down the video by 4 times, take over a dozen measurements, and then convert the average time for 25% speed to 100% speed time. The final result was a time of just 0.2925 seconds and a velocity of 39.34 m/s — around 88 mph!

I wasn’t finished yet. Sure, Coyote is going fast, but it’s not ridiculously fast. I needed to prove how unrealistic and absurd this scene was, and if you watched the clip, you’ll know what I’m going at: his instant acceleration. When Coyote fires up his Acme rocket skates ($99.99 at your local illegal weapons dealer), he almost immediately accelerates to his top velocity of 39.34 m/s. Once again, I slowed down the clip and tried to time it...but I couldn’t. It was so fast that I could only get a max limit of <0.15 seconds for 25% speed, which is <0.0375 seconds in real time. When that estimate is plugged in with the already calculated velocity, I get Coyote’s acceleration...of at least 1.049 km/s^2. That’s creating G-forces of over 100 gees! And keep in mind, that’s his minimum possible acceleration. I knew it would be ridiculous, but not potentially greater than that of the Roadrunner himself!

Wait a minute...I don’t even know the velocity and acceleration of the Roadrunner. 

...it looks like I’ve got another mathematical investigation for this weekend. 

[CatastrophicFailure]

14 minutes ago, ProtoJeb21 said:

The final result was a time of just 0.2925 seconds and a velocity of 39.34 m/s — around 88 mph!

You’re measuring the wrong metric here, clearly he just tripped his flux capacitor and is not changing velocity but warping spacetime around himself.  

[qzgy]

52 minutes ago, ProtoJeb21 said:

.but I couldn’t. It was so fast that I could only get a max limit of <0.15 seconds for 25% speed, which is <0.0375 seconds in real time.

Hey uhh suggestion here - why not just do frame counting? On youtube you can advance frame by frame with the period (.) and comma (,) keys. In the clip posted, he goes from standstill to having the rockets at full speed in 1 frame. Given that the clip has 24 fps, thats about 0.0417 seconds. So your measurement (presumably done with a stopwatch) does actually come relatively close to the value posted.

Warning - Contains kinda bad physics.

Spoiler

Now as @CatastrophicFailure will know, many of us like to do arbitrary math for such problems such as myself. I gave a shot at finding the speed of Wile E. Coyote, but using a different method. Between 0:39 and 0:53, he completes a complete fall up and down. Now whats great is that he's stopped completely at the top as if just being dropped. Counting off 167 frames (or 6.9583 s), he falls that entire distance (to first impact, when the cloud appears). Assuming standard earth gravity and using (hopefully correctly) applied 9th grade physics, that means he fell a distance of 237.4 meters. Because energy is conserved, his speed at going up (assuming 100% efficient transfer and no actual help from rocket thrust (which I assume there isn't in the vertical plane because.... magic? and there is no motion from Wile's legs when the rockets are pointed almost straight up) must equal the potential energy he fell. This works out using v=sqrt(2gh) to be 68.2 m/s or152 mph. Not bad! This is of course on the assumption he went up the same distance as he fell. If he didn't this is moot.

This is actually a much worse way as it relies on a number of assumptions about the conditions, but eh was a fun distraction.

Now uhh of course, we can also try and figure out his speed using that insane rocket skate acceleration and the terminal velocity equation (shamelessly googled). Using that and some approximated values (density of air is 1.2 kg per meter cubed, weight of Wile at 20 kg [high end of coyote weight], drag coefficient of 1 [approximately human shaped], projected area of 0.5 m^2 [about 1/8th wide as tall, maybe a bit wider, so slightly exaggerated for reasonability in my mind] and acceleration of 983.5 m/s^2 (using @ProtoJeb21's speed)), we get a maximum velocity of....250 m/s! Now, if we assume Wile accelerated to my calculated speed of 68.2 m/s in the same amount of 1 frame of time counted, the acceleration is 1635 m/s^2 and would give Wile a max terminal velocity of 330 m/s! Almost supersonic there! If we then assume this is at 1000 m altitude (given the western deserty look and the fact that I think that tends to have some altitude? Maybe? IDK, dont come from there) the density is then only about 1 kg per meter cubed and Wile can achieve a max speed of 361 m/s! Might be fast enough to break the sound barrier.

Of course, we dont actually know if Wile ever achieves max velocity so who knows. Also, cartoon physics.

Conclusion - He might be able to go really fast. That must be then a really fast roadrunner.

 

[Green Baron]

8 hours ago, 0111narwhalz said:

Not sure what you're noping here.

There are quite a few different forms of siege engines and catapults, driven by gravity as the one in the picture, torsion of for example leather straps or by tension unloading with a bow. The throwing component of a the ballista type thingy is actually a bow. Which can theoretically be made of leaf springs. It is only, steel didn't exist and iron is too brittle for that.

Edited October 18, 2018 by Green Baron

[0111narwhalz]

53 minutes ago, Green Baron said:

There are quite a few different forms of siege engines and catapults, driven by gravity as the one in the picture, torsion of for example leather straps or by tension unloading with a bow. The throwing component of a the ballista type thingy is actually a bow. Which can theoretically be made of leaf springs. It is only, steel didn't exist and iron is too brittle for that.

My confusion was born from the fact that my query was in the form "A or B," and the answer was a simple negative. Which I suppose could be interpreted as "no to both" or, equivalently, "the expression A OR B evaluates to false." But it could also be interpreted as "not A" or "not B," and it's not immediately clear which "nope" was intended.

[Green Baron]

So, "Nope", a ballista does not have to be propelled by gravity. But "Yep", it can be driven by a bow made of leaf springs.

--------------

Which reminds me of a funny or(logic or, can be both) interesting thing a friend once told me. When she studied computer science, there was a professor who lectured on propositional logic. In his speech he appended german "nicht wahr ?", "not true ?" - which is best translated as "isn't it ?" - to every second sentence and sometimes in between.

Which made it difficult to follow his examples because, in propositional logic, it negated everything he said before and, in speech, there are no brackets .... :-)

Edited October 18, 2018 by Green Baron

[p1t1o]

1 hour ago, Green Baron said:

Which reminds me of a funny or(logic or, can be both) interesting thing a friend once told me. When she studied computer science, there was a professor who lectured on propositional logic. In his speech he appended german "nicht wahr ?", "not true ?" - which is best translated as "isn't it ?" - to every second sentence and sometimes in between.

Which made it difficult to follow his examples because, in propositional logic, it negated everything he said before and, in speech, there are no brackets .... :-)

Thats so weird. What you are describing is 90's Northern England teen slang, except they would use the contraction "innit".

"You know like when becky was dating darren, innit, and then he went with Laura to the dance like innit, and they were making out by the fountian inniiiiiit."

https://www.urbandictionary.com/define.php?term=innit

 

Edited October 18, 2018 by p1t1o

[DarkOwl57]

12 hours ago, 0111narwhalz said:

Not sure what you're noping here.

No ballistias. Trebuchets or Catapults only

 

[tater]

Went to Gallup, NM, today. My wife had to be an expert witness in a lawsuit, so I drove her the 2 hours, and we made a day of it. Awesome early lunch at a hole in the wall. About to head back to ABQ.

[qzgy]

11 hours ago, DarkOwl57 said:

No ballistias. Trebuchets or Catapults only

 

Still think howitzers, cannons, and mortars would have been funner

Anyways, I heard about this neat trebuchet design. Might interest you. https://www.instructables.com/id/MURLIN-Trebuchet/

Its called a Murlin trebuchet. No idea why or what the efficiency is compared to a standard trebuchet, but uhh, yeah! Could be an interesting idea.

[Mad Rocket Scientist]

I assume you've seen this: http://virtualtrebuchet.com/#simulator

I made a roughly 1 m tall trebuchet using this out of PVC, but either the counterweight was a different weight, or I was exploiting some weirdness in the simulation since it needed a lot of tuning of the sling length to work.

[CatastrophicFailure]

2 hours ago, Mad Rocket Scientist said:

assume you've seen this: http://virtualtrebuchet.com/#simulator

Noice! 

I made an enormous trebuchet that can fling a dead cow over almost 2500 feet!

and then broke the sim and it won’t work anymore 

“Here comes Bessie...”

Now, to site my granary!