Are there gas power stations that generate steam rather than operating gas turbines?

Sunlight can be a useful tool for sterilising things. For example you can sterilise water by leaving it in bright sunlight in a plastic bottle. Or you can put a mattress in the sun to reduce the number of mites in it.

Think about how sunlight bleaches fabrics and other materials that are left out for an extended period - that is the same mechanism at work.

The easiest way to see the effect of uncertainties in a calculation is to redo the sums with the extreme values of the range.

So let’s say your average value was 20cm^3 per 10 seconds. The limits are:

20 - 1 = 19cm^3 per 10 seconds = 19 x 6 = 114 cm^3 per minute

20 + 1 = 21cm^3 per 10 seconds etc

This also helps to see how uncertainties combine, by considering all the limits that affect the final result in the same direction, although as another commenter alluded to, you don’t necessarily need to combine all your uncertainties linearly.

What do you mean by change position?

The gas turbine (jet engine) has an output shaft. This goes into a gearbox which drives the rotor and tail rotor. The helicopter turns by changing the pitch of the tail rotor, and so the sideways force at the end of the boom.

The vendor can check with the bank during contactless transactions, but there is no obligation to do so.

The payment can be cleared in real time, but doesn’t have to be. And if the payment is cleared in real time then a contactless payment will take just as long as a chip and pin transaction (minus the human faff).

The threat of being caught after the fact. The scammer has to perform the scam in person and will most likely be on CCTV.

Interesting, I have never experienced that. Here in the UK a debit card is associated with a single account, and savings accounts don’t have cards (typically).

What do you mean by select which account you are using?

You are welcome

There are advantages to building statically determinate structures beyond the simplicity of analysis; mostly related to the lack of prestress which means you can get away with larger manufacturing tolerances.

However in practice it is hard to achieve a truly determinate structure, and in many cases it is not necessary to even attempt it. There are analysis techniques that apply to indeterminate structures so it’s not like we just build those blindly and hope for the best.

The time is not spent by the machine communicating with the card. When you do chip and pin the card machine is communicating with the bank or credit card provider, and checking that the card is genuine and can afford the payment. This takes non-negligible time. In a contactless payment the vendor doesn’t check the card and just takes a risk that it isn’t genuine. The transaction will be settled up at the end of the day. This is why there are generally limits on the value of transaction that you can do contactlessly; it protects the vendor from being left out of pocket for a large sum.

Edit: this answer is Eurocentric. I understand that the technology may be different in other places, though in that case I doubt there would be a noticeable difference in speed.

Imagine four rods joined together with hinges to form a square. This structure is underconstrained; it can flip about into a rhombus. Now imagine you add an extra rod across the diagonal; the structure is precisely constrained and becomes rigid. It doesn’t matter what length the diagonal rod is (within limits), there will still be a single shape that the structure adopts. Now imagine you add another rod across the other diagonal. This structure is overconstrained; if the extra rod is slightly the wrong length then you will have to force it into position, distorting the structure.

The setup with one diagonal is statically determinate; it has the correct number of links and so cannot have any internal stress without an externally applied load. Importantly, if you apply an external load (for example pulling two opposite corners apart) then you can work out how that load is shared between the links and how much tension or compression each link experiences.

The example with two diagonal links is statically indeterminate, it may have internal stresses, and when an external load is applied you cannot trivially determine how that load is shared by the various links. This was very important when structures were designed by hand; it is much easier to work out how strong each member of a bridge truss needs to be if that truss is statically determinate.

There are mathematical ways of working out if a structure is statically determinate; basically the number of constraints must equal the number of degrees of freedom. But I find it much easier just to consider the intuitive examples.

Shockwaves do not behave the same as sound waves. For example they move faster with higher amplitude which is not true for sound.

It still isn’t the noise but the shockwave from the explosion that is the trigger.

You absolutely could implement a turbine rather than an orifice to drop the pressure of the fluid in a phase change cycle, and in doing so you would recover some energy that is otherwise lost. However the added complexity and maintenance overhead is not worthwhile in many real world situations such as domestic refrigerators.

Thermodynamic efficiency is only one of several competing criteria. Another commenter already mentioned that the size of heat exchangers is massively lower in a system with liquid than a purely gas heat cycle. This is far more important than you might think, given the packaging constraints of say a domestic refrigerator.

Yes governments can make money disappear, they do so by raising taxes and so taking money out of the economy, or by issuing bonds. These are loans to the government and so the amount that organisations give the government to buy the bonds has left the economy.

They can’t exactly do the same with student debt because it totals to zero overall. There is $1.6 trillion in debt but that is balanced by $1.6 trillion in cash that was paid to the universities etc.

If the government paid off everyone’s student debt then they would actually be adding more money into the economy; the money they would have to pay the owners of the debt (the lenders). They could in theory just cancel the debt and tell the lenders that they are shit out of luck, but that would make those lenders very angry, and would seriously destabilise any economy.

There is a difference between hypothesising something that could be observed, we just don’t have the means yet, and hypothesising something which is fundamentally unobservable.

It means: if I push against you, you are also pushing against me. A book on a table is held up by the table, and so it must also push down on the table. If a bullet is pushed forward by a gun then the gun must also be pushed back, which we call recoil.

The real trick is that governments actually auction bonds rather than selling them at a fixed price, so the market decides what they are worth at that moment. Typically though they choose a coupon rate (the percentage quoted) which matches market yields so that the bonds sell at or close to the nominal value.