Demand forecasting. That stuff almost all gets sold before it goes bad. American grocery stores sell a lot of food. Shipments come in daily

Ohhhh! I thought those regular ones were lower numbers (like 3s). This clears things up! Thanks.

Just to add this good explanation...

So if you focus on a specific point, objects closer than that point will blur as they get closer, and similarly objects further away will blur as distance increases.

The range of distances over which you have acceptable focus is known as 'Depth of Field' (or DoF) and it's affected by two factors: 1.> How far away you are focusing (the further away you focus, the larger the DoF) and 2.> The size of the aperture (e.g. iris or a gap in your fingers) through which you're looking (the smaller the aperture, the larger the DoF - this is for the reasons explained by u/waitforthestopsign)

The DoF is not symmetrical - in fact objects closer to you than the focal point quickly blur (but we tend not to notice because these objects are often in our peripheral vision); objects further away than the focal point blur more slowly as distance increases.

A consequence of this is that in very bright light the iris in our eyes contracts to limit the amount of light entering the eye, which has the effect of increasing the DoF and makes it much easier for the lens to focus - this is because it the lens doesn't need to be as accurate, and deficiencies in the lens (e.g. long-sightedness) become less noticeable. The effect is particularly noticeable on objects that are close to us which is one reason why reading in good light can be so much easier that in poor light.

To add to this, most people die with some cancerous growth in their body that had no effect on them. Not every cancer is going to be lethal or even harm you significantly because you'll be dead by the time it reaches that point. This video does a great job at explaining https://www.youtube.com/watch?v=yNzQ_sLGIuA.

Worldwide, there are on average about three or four 5.0-5.9 magnitude earthquakes every single day. They are usually not destructive (or not very destructive) and don’t kill anyone. It’s just that these relatively small earthquakes are now getting reported in the media all the time because of the recent big one that was very destructive and killed a lot of people. And there is no wonder that a known seismically active zone keeps getting them.

I worked at a rural wal mart unloading trucks. We averaged 3 trucks of GM and two fridge trucks on the grocery side per day.

What do you think the ones in town are doing?

They roll that stock constantly. Retail runs on very tight margins and they have logistics down to a quite literal science.

Assume you're talking about major stores (Walmart etc).

The US supply chain for these stores are some of the most sophisticated and efficient in the world. Waste is fairly minimal. These are stores with very low profit margins.

The US supply chain is an early adopter of many technologies. Well before anyone had wi-fi or laptop computers, stores used barcodes, wireless telecommunications and very sophisticated planning and inventory systems. Major stores use very advanced logistics and computer models in their supply chains.

It's called demand forecasting.

They look at: Current inventory levels. Outstanding purchase orders. Historical trendlines. Forecasting period requirements. Expected demand and seasonality. Maximum possible stock levels. Sales trends and velocity.

There's waste, but softwares account for that and maximum profit is the ultimate goal.

E-jets and most business jets have tail mounted engines. the reason is mission. tail mounted engines let you have short landing gear and less chance of FOD damage on crappy airstrips. this lets you load pax and cargo with out needing extra equipment. even with under wing engines if you look at the 737 vs A320. the original 737 used turbo jets so they could keep the gear as short as possible when they change it to the CFM's they had relocate the some of the pumps and you ended up with the hamster pouch nacelles to keep the low gear. Airbus when they built the A320 years later airport infrastructure had improved a ton so they just keep the gear taller.

Brakes. The gear differences between manual and automatic aren’t meaningful to slowing tire rotation. Limiting factors will be tire traction and brake strength, obviously including mass or vehicle.

Plastic from the bottles leach into the water overtime. Essentially, the expiration date is the estimation when the concentration of plastics in the water reaches a point where it’s no longer safe for human consumption.

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Everything gets a best by date also best by dates need to be within a certain length of time even though things like caned food are fine as long as the can is still sealed.

You can take an engine that makes 50lbft of torque and make it output astonishing amounts of power at the wheels.

All it takes is gearing.

A lot of people don't realize this. If your car with 300lbft of torque at 2000RPM is geared so that it can go 20 miles per hour at that speed, it's going to output the same power to the wheels as an engine that makes 50lbft of torque that is geared to go ~3.3mph at that speed.

It just won't go nearly as fast.

Grocery stores know very well from experience how much food they are going to sell each day and plan accordingly. There isn’t much food going to waste really. The stores keep a lot of food on the shelves because it looks good that way (and is arguably convenient for the customers).

*braking, *brakes

I've ridden bikes for a long time and without an ABS system it's a very delicate balance between engine braking, front brakes and rear brakes to maximize your braking.

But the difference with ABS is ridiculous. ABS is pretty much when you hit those brakes you stop and do so without without locking up. Fully pulling on ABS brakes on a bike is pretty scary even though it's relatively safe.

The same applies to cars except you have less danger of locking up or swerving. Without ABS you can combo down gear, brake pedal and emergency brakes for maximum effect.

But with an ABS system you really only need to jam down on the brake pedal.

I don't think there is a clear answer. ABS works by pumping the brakes very fast. It doesn't necessarily stop you faster than locked brakes. Instead it provides steering control authority while you are coming to a stop. The questions then become: does a fresh piece of tire brake better than a piece of tire that is getting hot from sliding friction? Does the act of rolling the tire reduce the effective speed of the sliding part of the friction equation (because the slower you are moving the faster you come to a stop)? I don't think both ABS and engine braking in combination would affect the stopping distance because you are already locking the wheels up as much as the ABS system allows but there might be an advantage to agressive downshifting because the tires continue rolling and that might reduce the sliding component force the wheels need to overcome more effectively than the ABS does by pumping the brakes.

I don't think so. The inertia of the engine and the rate of engine braking means a set of brakes will slow the wheels way faster than the engine would lose speed, which means you'd theoretically brake slower, because the engine still wants to rotate at a higher speed.

However, the brakes are also going to be strong enough to lock the wheels even when the motor's still trying to turn the wheels, and ABS will kick in anyway.

Typically, a set of good brakes will have many times more braking power than the same car's engine has motor power. Your brakes could take an engine from full power to stalled in a second (and probably ruin your drive train in the process).

The reason depends on your "mission" . Underwing engines let you have bigger more efficient engines. This also make maintenance easier. The down side is you need long landing gear and they could suck stuff in when on the ground. This puts the aircraft body higher off the ground so you need extra stuff to get people and cargo in and out. So if you need your aircraft to be low to the ground or take off from dirt or grass you have to mount your engines up high. This why lot smaller jets have the engines mounted up on the tail. Down side is this also limits how big they can be, but now your aircraft can sit lower to the ground and not need things like a jet-bridge or extra equipment to load cargo.

Something to note is when you look at aircraft like the older 737 and A320. Boeing wanted to make the 737 as low to the ground as they could wile keeping under wing engines. This is why they have that odd pouch shape. Airbus just keep the landing gear longer. 737 was designed with the idea that could go in airports that might not have the gear to load cargo in to a taller aircraft. Also the newer regional jet tend to have engines back on the tail. same thing they need to be go in to airports with out jet-bridges.

No it wouldn't. Gasoline vehicle engines are designed for higher RPMs and don't make peak power until higher up in their operating range. Tractor engines are designed for low RPM operation and have their peak power waaaaay down in the RPM range.

Emergency vehicles have the budget to do regular maintenance. Pushing the engines harder is less of an issue when you get regular check ups and maintenance to ensure reliable operation.

Almost all cars are limited by the tyre grip for how fast they can de-accelerate. Putting bigger breaks or adding engine braking power won't have impact on how quickly you come to a stop.

I'm not sure how well regular cars are at brake balance between the front and rear, so in theory if the rear wheels do very little braking you could stop a bit slower if you drive a rear wheel drive car and do some additional engine braking. But around 80% of the braking is done by the front wheels so it won't be that helpful.

Perpetual motion is impossible because of the law of conservation of energy. Even if we had a wheel spinning for centuries, we would never be able to pull more energy out than the wheel itself has. The "servicing" in this case would be speeding the wheel back up, but that would take energy. If we wanted to, we could keep the wheel spinning for as long as we wanted, but that doesn't make it into a power source.

Car brakes are good enough these days to apply maximum braking force short of locking up in almost any situation. ABS then means you can just stomp on the brakes for the best result. The exception would be if your brakes were failing due to overuse, say on a long steep descent. In that case you should have been changing down gears to use engine braking to prevent the brakes from overheating in the first place. You can do that even with an automatic gearbox. In an emergency stopping situation, even the best driver is going to struggle to shift down fast enough to help, short of real flappy paddle gear changing and/or extremely high speeds.