Useful to know that sometimes with escape velocity they don't give you "M" and you have to derive a different expression with the data given that can be rewritten as =GM allowing you to solve the equation. So they might give you the radius of the orbit of a satellite above earth and you need to use the value for the force per unit mass on earth due to gravity to derive an expression for GM. This might sound confusing because I don't remember exactly how to do it, just worth knowing you might not be given M in the question.
Einstein energy-mass equation for photon (m=0): E² = m²c⁴ + p²c² = p²c² This is useful if they ask you to find the momentum of a photon given the energy.
Its so useful to be able to derive some of these (equating circular motion with gravitational force to find Kepler's 3rd law or using coulombs law to derive other equations for charged particles like in a velocity selector, equating GPE with KE to find the equation for escape velocity, deriving the pV = (1/3)NMC^2 equation from the ideal gas model using conservation of momentum in an elastic collision and modelling 1/3 of particles travelling in each axis etc.)
A small correction, for dicharging the capacitor, the equation for current should include a negative sign (I=-Ioe^-t/rc) since the polarity has changed. Other than that these are quite helpful, thank you!
and also example or explanation of more usage of the formulae for the waves would be much appreciated (even a link to the related videos would be useful)
Absolutely Beautiful! You are amazing. I just want to ask 3 simple but very important questions to clear some confusion: 1 - When finding answers to certain degrees/figures, can we write our degree in the answer box next to the answer (e.g. Answer........40..(2.s.f).. N) 2 - Do you always give your answers to the same degree of figures as the values that they give you? I have been checking mark schemes and they sometimes give answers to different degrees. 3 - Does your answer always have to be EXACTLY like the mark scheme answer? Or is there a level of tolerance for every questions? Thank you so much Physics digita...I mean Online!
1) ? 2) Yes you always give your answer to the same sig f as the numbers in the question unless they specifically say so. The Mark Scheme rarely ever let's you off and you wont know when it will 3) You can use a different method if it is "Correct Physics". Sometimes people use incorrect physics, e.g. When working out the Gravitational Potential for a mass outside of earth in field, you can't use mgh. Let's say you were told to calculate efficiency of a system and you calculated it using "Power" instead of "Energy", this is fine even if the markscheme used "Energy" to do this
I think he’s talking about when it’s open questions and you have to explain something. Does it have to be exactly as the mark scheme or can it be along the lines of it(with main concept and main definitions in the answer)
A general rule of thumb is to use the LOWEST number of sig fig out of any of the numbers you used in the calculation. E.g. if you're doing F = ma, with a given mass of 2800 kg and acceleration of 1.25ms^-2, it's safest to use 2sf, as 2800kg is given to 2sf, so you can't be assured of any precision beyond that. This doesn't matter too much for most questions, but if they ask for an appropriate number of sf, this is the sort of thing they mean. And I don't think they really mind if you put the degree of rounding in the answer box, but I generally just leave it there in the working out, and then put the rounded answer alone in the box. And there's generally some tolerance, yes. If your answer is to a somewhat appropriate number of sf (3's always a good shout), and rounds to the one they have, that should be alright I reckon. Some questions are harsher about this. A good skill to have is knowing how to store numbers on your calculator - this reduces the risk of any significant rounding errors during working, as you shouldn't really be rounding early.
For Oxford AQA, if you are asked to show something is approximately a value e.g. show the resistance is approximately 53 ohms, your final value should be at least 1 sig fig more than what the question has shown. For the above example, if your final answer is 52.918182… then round to at least 3sf
11:02 was going to ask - takes a sheer amount of potential to write the other way around at that speed sir, quite admirable ahah - I was humbled real quick!!
I can't find anything in the AQA spec but we've been taught to use 273.15 and on all the revision sites it says the same so I would (and will) use it with the .15.
You could. I’ve always found that the numbers are so large, and the temperature your converting from is usually given to a whole number, that using this figure to 5sf is a bit unnecessary.
@@kingzmash9124 At 11:07 when he flips it, that is what the camera sees. The writing looks so bright because put simply, its glass/pastic which as light shining into the side of it from all angles. I don't think there is much else to it except that.
Pretty helpful, as usual. Is there a video on this channel going over uncertainties in more depth? Also, I've got a q. I could've sworn I saw something somewhere which said the uncertainty in the gradient is the difference between the 2 worst fit lines divided by 2, and the same for any intercept. Is this also valid? Also, I feel like the MS also said something about estimating the actual gradient as the average of the 2 worst fit lines (instead of eyeballing an actual best fit line ig). Is this fine, too?
Hi there, your videos are super helpful in my a level revision so thank you much. PS I believe that the diffraction grating equation dsin θ = n λ is not on the formula book but is very important. PPS sorry if this is in the video and I just missed it but as far as I can tell it isn't
I am not the only one wondering how on Earth he is writing backwards right?? like he has to be writing the mirror image of what we are seeing from the way he is writing right? or where is the camera positioned to be able to film this if he is in fact writing it normally??
