studiot

When your original post is fit for other members to draw from perhaps you would like to explain what underlies your link between gravitation and inertia. The two are currently regarded as different independant phenomena and the fact that, as far as we have been able to determine, they offer the same values is just a fortuituous accident of the unverse.

I would have thougth any parent or grandparent would have first hand experience. Facilities for games, school dinners, practical subjects like woodwork, science are regularly being sold off by schools around the UK and have been for some decades. Some universities now use circuit simulation only instead of hands on electronics, mechanics etc. Or else, like Exeter they have simply closed the Chemistry department.

With the accountants and centralists now firmly in charge of education would members like to comment on the trend to reduce or even remove all practicals from the curriculum at all levels from primary to university. How is this impacted by the current expanding crop of 'demonstartion videos on Ytube and the like ?

Yes of course, but just be glad you are studying under the MKS metric system. There is also a unit of force called the kilogram-force or alternatively kilogram-weight. https://en.wikipedia.org/wiki/Kilogram-force This short tutorial may also help BBC BitesizeWeight and mass - Forces and movement - KS3 Physics - BBC...Weight and mass are very different. Find out more with BBC Bitesize. For students between the ages of 11 and 14.

I understand and sympathise with your need to obtain marks. Perhs you could discuss the issues with you teacher ? Remember I said you have to start somewhere, you can't do it all at once. So teachers will not tell you everything at once, (I haven't done that either) but good teachers will take the time to explain further to those, like yourself, who are interested enough and intelligent enough to know a bit more. Mass is one way of measuring the quantity of matter in a body. This definition becomes important when studying forces and dynamics.

Then I agree with you that the question was poorly worded, especially as it was an exam question. I also agee that it was not clear what force they were asking for since you have evidently been taught to distinguish. However there is also not enough information to answer the question since I would assume (as any schoolboy and KJW) that the object was on Earth since we are not told otherwise. KJW's diagram relies on gravity so there must be a third force acting on the spring balance if we take that as the object. This, of course would be the weight, W, of the balance . But KJW asked for the reading not the force acting, and there is a difference. Since you have come across vectors can you say anything about the vector sum of the two or three forces that are acting ? Did you also understand the difference between the two equations I wrote for you? Have you come across the equation W = mass x g = mg ? Finally can you think of another distributed force ? This becomes important in situations where no one in their right minds would say that a pair of equal and opposing distributed forces mean zero force on an object. Hopefully this discussion is helpful.

Thank you for responding, with that useful information. +1 I asked because I am trying to be careful to avoid messing up your programme of study. You have clearly picked up on something, perhaps as swansont said it was just a poorly worded question. Were these the exact words of the question and nothing else ? +1 to KJW for the excellent sketch, I for one have not seen before, but so obvious when posted. So we come to that word 'vector' that I avoided, but both the other responders used. Forces are usually introduced (in basic Physics) before vectors are introduced and often used a lead-in to vectors. Have you come across vectors yet ? In my day forces were introduced by way of a spring balance, like KJWs picture. The whole class has a competition to see who could pull out the spring balance the furthest. Vectors were not introduced until advanced school physics, and later still in Mathematics where they were introduced by way of velocity. Yes "Force is a push or a pull" is a good start. The thing is that there are several thing you need to know at once about forces and your teachers have made a good start with with contact/non-contact and balanced/unbalanced. The spring balance is good because it shows any Force has four particular important characteristics. A line of action - more particularly a straight line of action. A magnitude or numerical value. A direction along that line. A point of application. Vectors are more general and do not necessarily have a point of application, as for example velocity is a vector without a point of application. I will add one more thought to your contact/non-contact idea. In order to represent all forces in the format of my items 1 - 4 we also distinguish body forces such as gravity which are distributed throughout the body and introduce the 'point of action or application' as a 'centre' the COG or cnetre of gravity in the case of gravity. The force of gravity is often excluded, either deliberately or just forgotton, as in the case of the question "What is the force on a book lying on a table ?" With the foregoing the student is well equipped to study lots more mechanics including Newton's Laws, equilibrium, net force', ' resultant force', 'total force', and so on. ~With this study will come some mathematics - equations and the like. Depending upon the format of these equations and the mathematical sign conventions used your original question can be presented in several ways. Assuming no other forces acting (excluding gravity) Forces from the left = Forces from the right so your body is in equilibrium. 150N to the left = 150N to the right Alternatively with the convention forces to the right are positive The sum of all forces = 0 so your body is in equilibrium. -(150N) + 150N = 0 Does this help ?

Without seeing the question it is impossible to tell. Strictly speaking neither zero nor 300 N can be correct but there must be more to it that meets the eye. Where was this question and what are you studying ? What do you know about forces ?

Had I seen that report I could have said I left that for you.

The mathematical term 'group' (originally from the german) is just not appropriate for this purpose. There are other group axioms which the model does not comply with.

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But sometimes he is piercingly perceptive and I for one wish to encourage that side of him. No attack, its just properly conducted discussion. However if you are using a mathematical group you do not have the luxury of a point of view. Element uniqueness is part of the definition. The real number form an infinite group and every one of them is different. My query, and I believe that of dimreepr, was that the OP has claimed that repetition (or copying) must occur because the universe is infinite.. This is not so. Perhaps there is confusion between Cantor's definition of an infinite set as one in which each subset can be mapped one-to-one to the entire set, for example the interval (0, 1) contains the same quantity of points as the whole real line but it is in no way the same or a copy.

Please explain the purpose of your enquiry. Is it for cosmology as has so far been assumed or the alternative geological hypothesis about plate tectonics being due to the Earth shrinking, or what ?

Did you have a reason gor this ? If so please share it. Yes this is true but so what ? It is also a fundamental property / characteristic of any group, finite or infinite, that each and every element of the group is unique. Certainly not a property the OP has endowed his model with.

That may well be so, and indeed MigL has pointed you at KT's work. But it does not answer the question I actually asked about absolute time. I added a couple of lines of explanation, what did you not understand about them ?

Oil would be extracted, processed, stored and distributed, all of which involve a CO2 cost. The on board absorbtion process would not only involve space for the necessary plant, but obviously greatly increase the fuel requirement for journey. Yes the conversion to carbonate would offset the CO2 generated but it is obvious that cargo capacity of the ship would be greatly reduced and other not offset costs would be involved.

Seconded +1 How is this supported by this ? Surely the way you have described wormholes assumes and absolute time throughout the superuniverse ? Which is definitely not in accordance with Einstein's equations.

Sounds to me like a typical account's greenwashing. CaO + CO2 = CaCO3 56 + 44 = 100 So for every ton of carbon dioxide removed from the fuel, the ship will have to carry 1.3 tons of calcium oxide and make space for 2.3 tons of carbonate storage. And carbon dioxide is a very significant proportion of the weight of the fuel. If the 2.3 tons is then 'dumped' at some location outside the home port or country it will not count there.

So it's a pretty pointless exercise then, without at least some specifics. In any event you have contradicted yourself a couple of lines further on by starting with a 'who' Actually if there are only 2 parts to creationisy theory it is missing at least one vital ingredient. If something is being 'created' what is it being created from ?

It seems that the disbenefits of our own private oort cloud are piling up. It only takes a microgram of asbestos to cause cancer. How do you know that graphene is not similar? Many cities on earth are now suffering from 'particulates' in the air seriously affecting the health of the population there. Then there are the geological aspects of this. It is true that sufficiently large volcanic eruptions or meteor impact can throw enough fine ash into the upper atmousphere to cause global temperature reductions. As far as we know these temperature effect last from a few years to a decade or so. But the erffects on the population of the planet has been more dramatic, from example exterminating the dinosaurs. Also we are overdue for the next ice age, when we will need all the sunlight we can get. So if we put too much material up or need to bring it down again (in a hurry) how would we do this ? What happens if we get the right amount but then another volcano puts up more, tipping the balance into ice age ?

Are you vaware that by the time you have put up 50,000 tons of powder into low earth orbit, you will actually have use something like 750,000 tons of fuel and also put up something like another 50,000 tons of rocket?

1) Why graphene, not ordinary carbon ? 2) Fine to nano sized particles will filter down to ground level. What about halth risks to humand (or other species) ? Remember coal dust, silaca dust, asbestos dusk scandals ? 3) Carbon particles of any sort block the insolation by absorbtion, not reflection. So if the proposed layer is below the cloud the energy will still be confined to earth. Sunshades themselves get hot.

I missed this thread first time round, so thnaks for the update. Super. +1

Yes but this thread is very firmly in the Physics section. Variables in Physics usually have physical dimensions, and that includes the variables in the 'wave function', which is a physical quantity of interest. Probability is a dimensionless variable. Furthermore even non dimensional varaibles in maths may have different domains and certainly different codomains. This is not trivial since 0< P(x) < 1 at any measurement and the whole measure = 1.

The wave function is not a variable it is called the 'wave function' because it is .. a function. I agree and said this earlier in the thread. Classical probability is a limit to infinity. As a result we have to make do with the best estimators we can.