Why does it take 2 bags?

[rockouthippie]

I figured out a while ago that I couldn't take 2 16 oz cans of pop and hang it off the handle bars on my bike. The bag would rip and fall on the ground. I have to double bag it. It's not even close. Obviously would rip out.

But I can put 4 cans in a double bag, and it doesn't rip. No evidence that it would rip at all.

Why?

[SSJ4 Gogitta]

Better question; what kind of shitty plastic bags do you get that can't handle 32oz of soda? I can put damn near a 12 pack of 12oz cans in the bags we get here.

[fc*uk]

See, to reduce the plastic, we have reduced the effectiveness of the bag ...

Oregon cares, West Va. does not?

Same in FL too I am noticing ROH. Unfortunately, the use less plastic in the bag does not work because you need double the bags...

There is also a materials stress test behind what you have observed ROH, which I am skipping. Needless to say, yes, two does have more strength the one alone doubled.

[mike-db]

Haven't used plastic bags in a while, the store that I do most of my grocery shopping at has boycotted plastic bags all together and only use paper, needless to say I spent the couple bucks needed to buy their "brand name" reusable bags.

[fc*uk]

I'm impressed with Canada's reduction of plastic waste as a whole, Mike. I really wish that would appear in the US as well ...

[mike-db]

I had no idea, figured it was just common all around in the first world countries.

[. - .... .- -. ....]

In Ireland, and in a lot of Europe, plastic bags aren't handed out, but are levied. You want plastic bags, you pay 10-15 cents per bag. As a result, people buy or bring their own recyclable cloth bags to the store. Helps the environment, bags are much better, and people actually rake more responsibility for plastic bags and where that shit ends up.

[rockouthippie]

What's the big deal about plastic bags? The new ones are even biodegradable. They add baking soda to the plastic so it disintegrates in the weather. They are recyclable. If I think about it, I bring the old bags back to re-use.

And what's the deal with re-usable bags at $2 a pop? I'm in the wrong business.

Usually I just shop by bike, so I have 2 large panniers and don't use bags at all.

But it's like CFL light bulbs. I have two incandescent lights in the house. Now I gotta pay $5 a pop for "durable service" light bulbs... Made in America.. Just a freaking light bulb.

I can just see Pelosi and Reid bitching about my two normal light bulbs, then burning 2000 gallons of aviation gas getting their lard ass up in the air to screw with something else.

They didn't need to ban regular light bulbs. CFL's are great if you didn't want mood lighting in your dining room or didn't want to wait 5 minutes for the porch light to warm up. Why wouldn't you use them?

I didn't need a gun to my head. 4X less money for electricity and they last 5 years... I was already in.....

Terrific... unless you have a dimmer and unless it's the porch.

It's still not intuitive why 2 bags is so much stronger than one bag though. Or why Congress thought it was so important to mandate something people would and did adopt as a matter of common sense.

Just about everyone I know switched to mostly CFL's way before the ban on normal light bulbs.

You might have had to force me if we were talking about the early lights. They changed CFL designs though. Now they put a rectifier in them, so that the light runs at 120hz instead of 60. This doesn't give the fluorescent eye buzz like tubes and early CF's.

But can I have one 100 watt light on a dimmer in my dining room and a porch light without it being a federal offense?

Given that I have burned no gasoline so far this week, can I get a break? Home Depot is a little too far for a bike ride, so I'm gonna burn 2 gallons of gas going to get my "durable service" light bulb. I need one.

[mike-db]

Light bulb laws huh? I think something close to that effect happened up here, couldn't say.

With the re-usable $2 bags... Meh it's a couple bucks, where else is it going to end up? Under your drivers seat probably. (That's where I found my money for my bags) They sure are handy though, and fairly durable for $2.

To answer the original question to the best of my knowledge, why two bags? I have no clue. I remember having to double up for pop actually, but then again I usually always doubled up for liquids. I mean they are thin plastic bags. You should never trust anything that has thin or plastic in the same sentence for any sort of strength what-so-ever.

[rockouthippie]

I think plastic is better than paper. Paper wouldn't survive swinging on a handle bar, even if it was the $2 super-bag.

They'res a lot of stuff around to ban or tax this, that or the other thing. But I think most of us were already on board.

Maybe we should ban private jets. Pelosi and Reid have stepped off a private jet to bitch about my porch light.

[mike-db]

The $2 bags I speak of are not made of paper, they are bag's that are weather proof, re-usable in every way. Not sure what they are made of, easy enough to just keep them in the car.

[. - .... .- -. ....]

Originally Posted by mike-db

The $2 bags I speak of are not made of paper, they are bag's that are weather proof, re-usable in every way. Not sure what they are made of, easy enough to just keep them in the car.

Same here. The reusable carrier bags are actually made from recycled plastic themselves, and are heavy duty enough to last quite a while.

http://www.greenerimpact.com/wp-cont...re-of-them.jpg

rockouthippie, I guess the deal with plastic bags is that they are so ubiquitous, EVERYBODY uses them and I've seen first hand what they do to the environment, the water table, etc. I've pulled tonnes of the things out of natural water fissures where they's blocked water flow, so on and so forth. And even the biodegradable bags aren't biodegradable - they just break down into smaller pieces, and these smaller pieces take even longer to break down than a standard bag. The Great Pacific Garbage Patch is a prime example of where all this shit ends up.

http://en.wikipedia.org/wiki/Great_P..._Garbage_Patch

[rockouthippie]

The Great Pacific Garbage Patch is a prime example of where all this shit ends up.

How did my plastic bag end up in the ocean? Garbage goes out to the desert 350 miles from the coast. I am 90 miles from the ocean.

[. - .... .- -. ....]

Not sure if ditching garbage in the desert is a much better solution, but that's another story.

Your one specific plastic bag will never be a problem in itself - it's en masse where the problem arises. A quick google search shows that 380 billion plastic bags are used in the United States every year - thats a lot of pollution no matter what way you look at it. I don't see a problem in bringing the same heavy duty bags back to the store to reuse them on a weekly basis, if it means that a few less tonnes of shit end up in a landfill or in the ocean.

[. - .... .- -. ....]

Anyhow, to answer your original question:

Originally Posted by rockouthippie

I figured out a while ago that I couldn't take 2 16 oz cans of pop and hang it off the handle bars on my bike. The bag would rip and fall on the ground. I have to double bag it. It's not even close. Obviously would rip out.

But I can put 4 cans in a double bag, and it doesn't rip. No evidence that it would rip at all.

Why?

...I assume that is has to do with how the force is distributed around the bag(s). Pressure is the force per unit area applied in a direction perpendicular to the surface of an object, i.e. force/area, force itself being a product of mass and acceleration due to gravity. It's not going to be a linear relationship because doubling the number of cans in the bag (mass) doesn't double the pressure on the bag's surface - it spreads the force over a larger area. Therefore four cans in two bags will apply less pressure than two cans in one bag.

Additionally, with four cans, the bags are kept in tension, and can't bounce around. Two cans can bounce around (increase in acceleration and therefore force, and therefore pressure). So again, more pressure in the single bag with two cans, than in the double bags with four cans.

QED


O

[fc*uk]

My wife living in Toronto for the year kinda pushed us in a direction to reduce our plastic bag consumption. I believe Ontario charges $0.05 per bag. So, we bought big cloth ones as my wife did not have a car in Toronto.

Now that we are no longer there, we still have the cloth bags and a car. I keep the bags in my trunk and drag them into the grocery store. Hand em to the baggers and they just smile...

I've been told that the US is supposedly going to get onboard and start charging for plastic bags like all the other countries are doing. Right now some places will offer you some sort of a credit if you bring your own, but it has not gone much further than that.

[rockouthippie]

I remember smog. Before the car emissions testing and cleaner running cars made it less of a problem. The air over America is now cleaner than it ever was, and cleaner than anywhere else in the world.

But there is a problem. Now cars test themselves. Necessary in the 70's, but not anymore.

With any car later than 1990 or so, you'll get a big red idiot light when the car is polluting. If you ignore the light, you'll generally end up damaging the emissions system and end up with a car that won't run in pretty short order. Usually the cat converter turns into a brick and you don't have an exhaust system anymore.

I live about 12 miles from the Willamette River. It's still a toxic superfund site, but it's not from anything anyone did in my lifetime. It's from all the waste they dumped into the river 50-110 years ago when Portland was new.

So you got this floating garbage pile in the ocean. Since the composition of the plastics in the floating dump contain PCB's and no plastics for 20 years in the US do... it isn't my grocery sack out there floating in the ocean. If it is floating out there in the ocean, I don't see how ingesting non toxic plastics like grocery bags is gonna hurt anything.

6 pack rings were a problem, but we banned those. A good idea.

I don't see what difference "paper or plastic" makes. Like I said, my garbage goes out to the Eastern Oregon desert.

Now they want to charge a nickel for a bag that costs 1 cent. For our own good... oh brother.

People have made a lot of money making us greener. This wasn't an altogether bad thing. We are a lot cleaner than we were in 1970. But to stay in business.... I think our eco-lobby is now engaged in grasping at straws. Unlike 1970, I could go to Portland and not have my eyes bleed from the smog. The beaches look better. The "bottle bill" was the first in the country and did help roadside trash.

But we still need a multi-million dollar testing center to essentially look at the idiot light?

It's 2012. We should put our bra back on. We've been running around looking like a cow for 50 years. I'll point out that most of the original founders of organizations like the Sierra Club and Greenpeace have quit with prejudice.

Lacking anything to really be a problem, crying wolf seems to have worked until lately.

[swingdjted]

Originally Posted by . - .... .- -. ....

Anyhow, to answer your original question:



...I assume that is has to do with how the force is distributed around the bag(s). Pressure is the force per unit area applied in a direction perpendicular to the surface of an object, i.e. force/area, force itself being a product of mass and acceleration due to gravity. It's not going to be a linear relationship because doubling the number of cans in the bag (mass) doesn't double the pressure on the bag's surface - it spreads the force over a larger area. Therefore four cans in two bags will apply less pressure than two cans in one bag.

Additionally, with four cans, the bags are kept in tension, and can't bounce around. Two cans can bounce around (increase in acceleration and therefore force, and therefore pressure). So again, more pressure in the single bag with two cans, than in the double bags with four cans.

QED


O

Awesome. I love this reply. RoH's situation is something I noticed a long time ago, and I never really had a decent understanding of it. It's really amazing how much shit you can put into a double bag with no worries or issues, when far less than half of that shit ruins a single bag when you bounce it the first time.

[rockouthippie]

I don't think you can explain it by just the double surface support.

[swingdjted]

Not so much 2x bag surface overall, but rather twice the surface per grocery, since the groceries are spread out more.

Also, take a 100 pound object and a 200 pound object, with you alone trying to lift the 100 vs. you and a comparable-strength friend lifting the 200. Both are almost damagingly heavy, but it just seems a lot easier with the latter, maybe because of the balance and spread of weight. Not a perfect analogy, but still, there is a difference in distribution of weight, just like the bag example.

[rockouthippie]

Maybe?

It's a pendulum. 2 bags doesn't stretch out and rip out because the amplitude of the swing is less, dampened by the extra bag, not because the extra strength of the bag.

Maybe the extra bag sort of acts like a shock absorber.

[swingdjted]

I guess what Ethan and I are saying is that the cans aren't twice as heavy and the same number and size, but twice as many and the same weight each. Based on what we're saying, if there were still only 2 cans of the same size, but twice as heavy each, they'd probably still cause the same problem.

[. - .... .- -. ....]

Exactly. A linear increase in mass (x2), and linear increase in the thickness of plastic supporting the mass (x2) doesn't mean a linear increase in the forces involved. So doubling the number of cans and doubling the number of bags used doesn't "balance out", i.e. the force per unit area doesn't remain the same, but rather, decreases.