A Level Physics Revision: All of Gravitational Fields (in under 23 minutes)

[@esoterica3099]

" today we are going to be talking about a very attractive topic..." i see what you did there

[@zhelyo_physics]

what is physics without a good pun

[@esoterica3099]

@@zhelyo_physics haha so true, also sir your videos are extremely helpful. thank you so much :))

[@puddleduck1405]

Thanks!! I had a test on this and electric fields and got an A*, your videos and extremely useful! I'm gonna be watching the nuclear physics videos over the weekend as I have on that next week :)

[@zhelyo_physics]

well done on the A*! Amazing and thanks for the comment. If something doesn't make sense on the nuclear physics, drop a comment, good luck!

[@tobokanleya3348]

That pun at the beginning 😂

[@zhelyo_physics]

What is physics without puns : )

[@naveedhasan6738]

i thought i was the only one🤣

[@zhelyo_physics]

I am glad my puns are getting recognition! 😆

[@Hellothere-p7s]

What's pun

[@yeety1208]

​​@@Hellothere-p7s He said "a very attractive topic" (the hidden meaning is that the topic is about attractions due to gravity)

[@_Anti_Communist_]

Perfect Video! Paper 2 is coming soon so these types of videos do the job well. I like how you cover everything important, as I can easily follow along with my AQA textbook and everything key is mentioned by you. A textbook is good but it is an overwhelming amount of information, and videos like this one condense all the most valuable data into less than half an hour!

[@Amos-ks9yp]

I had an incredible pass on my exams after watching your videos l became a confident student because of your videos in physics although l used to stutter out my answers in class now l have boosted my knowldege through your videos and my stutter in class has improved much better because l now have the confidence of what l am saying to my fellow classmates and eventually l became the best student in phyiscs l just wanna say thank you Sir

[@zhelyo_physics]

Reading this honestly makes my day, thank you so much for sharing it and the comment!!!

[@umarazam1182]

thanks alot my class and I were having difficulty in A2 physics and this was really helpful ( recommended this channel to my whole school) thanks alot sir

[@zhelyo_physics]

Wow amazing! Thank you so much! Comments such as these genuienly make my day!! Thank you.

[@umarazam1182]

@@zhelyo_physics and teachers like you make our life better sir

[@cloverfields4]

These videos are amazing, thank you. I have a test in 3 days and this has really helped!

[@zhelyo_physics]

thanks a lot for the comment! Glad this is helpful and good luck on it!

[@neuropcs5879]

Incredibly useful video, much appreciated!

[@zhelyo_physics]

Glad it was helpful!

[@arcriciaslumingu5417]

Excellent videos please keep on the good work. Am benefiting a lot as a new A Level Physics teacher.

[@zhelyo_physics]

thanks a lot for the comment! Much appreciated! Drop me a comment if I can help in any way.

[@apple6112]

thank you so much for this intricately crafted video, this has genuinely helped me so much, even more then my school teachers who arent exactly the greatest...

[@zhelyo_physics]

Thank you so much for the comment!

[@whatchickens_]

Video was very helpful, thanks👍

[@zhelyo_physics]

anytime!

[@Bbbbbbbbbbhhhhhhh]

Man, I’m here after struggling like hell with this topic even though I know the equations. I always have problems with how to apply them. But we did only start the subject a few days ago.

[@zhelyo_physics]

Good effort! Drop a comment if anything doesn't make sense.

[@erino5432]

Great video thanks! Love the layout of the videos and really highlights key concepts/ equations! What if the centre of mass/ point mass is not inside the planet/ mass? E.g like a cartoon crescent moon, would g on one side of the surface be different?

[@graceogilby7961]

The centre of gravity is the point at which the weight APPEARS to act, so I'd assume the field is the same radial pattern about that point, just practically it obviously wouldn't work like a sphere. For example, at a centre of gravity which is outside the object, assuming no other forces act on you, you'd be suspended there because that's the point the force is pulling to.

[@theanimationmaster724]

17:06 small error, gravitation force should not be negative

[@akoterryeyong8259]

Your the best . 😭😭😭😭Thank you so much❤❤

[@zhelyo_physics]

anytime! thanks for the comment!

[@em8136]

When would you use gravitational potential instead of gravitational potential energy?

[@zhelyo_physics]

Excellent question. The gravitational potential is independent of the mass of the object that is experiencing it. In exams - chances are the question will probably ask and mention the potential. Otherwise anytime you want to map a gravitational field to have an idea of its characteristics without involving a mass m it acts on. Hope this makes sense!

[@em8136]

@@zhelyo_physics thank you. That makes alot of sense

[@crumpet55]

Are we expected to be able to recall the mass and radius of the earth? Thanks for the great video!

[@zhelyo_physics]

typically not. Btw, a good way to quickly rederive the mass if you know the radius, g=GM/r^2 set g=9.81 and if you know the radius you can work out the mass. The radius is typically given in the formula booklet but it can vary by exam board. Hope this helps!

[@mayagupta9948]

You're the best!!

[@zhelyo_physics]

thanks a lot for the kind comment!

[@gautammorkhandikar394]

As OCR do not give the value for radius and mass of the earth, can the exact values which you gave in the video be used in a question or are you required to work out these values?

[@zhelyo_physics]

Good question, if the values are not given in the question they will end up cancelling or you would be able to calculate them first. Generally I recommend not memorising those.

[@kannan2052]

What is the difference between the Point mass and the center of the Mass?

[@zhelyo_physics]

A point mass is assumed to have no size and many theoretical concepts in physics are solved with this idealization.You can even treat something as large as a giant star as a point mass in some cases. A collection of those point masses will have a center of mass.

[@kannan2052]

Okay, thank you!

[@datonebro613]

Sir thank you so much my teacher glossed this topic. I would like to ask if you could be able to cover just a couple of WJEC Eduqas equations? Eg the time period of orbit related to d^3. EDIT: includes the masses of both planets for a binary system.

[@zhelyo_physics]

anytime! Very interesting question. In those questions some things to remember are that: 1) time period is the same as the planets orbit the centre of mass for both planets (for a circular orbit); 2) the centripetal force and centripetal acceleration on both planets is the same by Newton's 3rd Law 3) the angular speed of both planets would be the same (assuming circular orbits)

[@datonebro613]

@@zhelyo_physics thank you, but just to clarify for the 3rd point, is the angular speed the same even if both bodies are different distances away from the center of mass? Or am I thinking of the angular velocity?

[@kannan2052]

You mentioned that G.P.E is -GMm/r but later in the G.P.E=K.E part, you took the G.P.E as GMm/r, so is it supposed to be negative or positive?

[@zhelyo_physics]

I really wish I could do this in vector form for A Level to avoid this confusion. If you are doing A Level Physics, think of it like this - it is negative, but when solving for r or anything where you need to square root - consider the magnitude only. Outside of the spec: F=GMm/r^2 x [r] where [r] is a 3 dimensional unit vector, to find the energy you take the integral of F with the dot product of dr which returns a scalar with no direction (sign problems). This bit is only relevant if you want to do physics at uni.

[@prodbymyles]

@@zhelyo_physics thank you for that, this is the only part I didn't understand of which I do now

[@kausarlolz]

hello sir! do we need to know about low level satellites or just geostationary for ocr a?

[@zhelyo_physics]

pretty much all satellite motion can appear with using either total energy of a satellite (GPE which is negative + KE) or using Kepler's third Law or also speed of an orbit of a satellite

[@nomadactual2484]

why is there a negative before GMm/r^2 here 3:36 but there is no negative over here 9:12 and here 20:51

[@zhelyo_physics]

unfortunately in A Level Physics the negative is included only to show that it's an attractive force (in some exam boards). Almost all questions take into account the magnitude only and if you are doing AQA physics the equation is given without the negative in the formula booklet. Hope this helps!

[@nomadactual2484]

@@zhelyo_physics what about edexcel?

[@plop.mp3246]

Hello sir, Could you please add this to your Gravitational Fields playlist, thank you!

[@zhelyo_physics]

will do!

[@juveria6536]

is keplers law included in syllabus now?

[@zhelyo_physics]

depends which exam board, but generally yes, please double check with your specification

[@juveria6536]

@@zhelyo_physics cambridge, CIE A LEVELS

[@peanutbuttah1391]

Why is g constant for small changes in height near the earths surface? (Cie syllabus) Do i mention about the field being uniform thats it?

[@zhelyo_physics]

so the field lines are only very very slightly curved near the surface due to the scale of the curveture of the Earth. Near it's surface we can assume the field lines to be parallel. Only near the surface though, if you are looking at astrophysics and the planet as a whole, you need to assume g varies with g=-GM/r^2. Hope this helps!

[@peanutbuttah1391]

@@zhelyo_physics Thank you so much

[@zhelyo_physics]

anytime!

[@thehudakhan]

is this for the cie 9702

[@zhelyo_physics]

for all exam boards, it is almost identical to 9702, I recommend downloading the spec and using it as a check list. Good luck revising!

[@matrixrbx]

Great video! Just a heads up, this video is missing from the overall topics playlist, here's a link to it: kzbin.info/aero/PLSygKZqfTjPC3hJ7nRSnnXTw3tI_o67dR it has pretty much every other video just this one is missing I think.

[@TheeFootballZone]

is this aqa spec?

[@zhelyo_physics]

Gravitation is almost identical at all exam boards so applicable to all. I always recommend having the spec at hand to use as a checklist. For some parts (particle physics and the AQA options) I have separate videos.

[@BarniDeDino]

W video

[@talalna12]

Is escape velocity also said to be orbital speed/velocity?

[@zhelyo_physics]

Hi, no the two are different. The orbital speed is under the speed of a satellite portion of this video and escape velocity under escape velocity. For orbital speed you equate the forces, for the escape velocity you equate the energies. Hope this helps!

[@talalna12]

@@zhelyo_physics Oh! Thank you so much for the reply 🙏

[@abdulrahmanur-rehman4715]

Hello Sir is this video still applicable to the new 2022-2024 CIE syllabus ?

[@zhelyo_physics]

Hi I haven't checked but the physics doesn't change. My best advice would be to download the spec and tick from the video as you are going along. This way you are in control of your own learning and you ensure you have covered everything. Hope this helps!

[@S_H-R]

Big fan sir Great video But where can we get notes ?

[@zhelyo_physics]

Thanks for the comment! Only videos are available I am afraid, I definitely recommend making your own notes using the syllabus and your own notes at hand.

[@S_H-R]

@@zhelyo_physics ok sir I hope for the success of this channel Keep it up

[@harvcoshy4551]

Why is there a double ad every minute. Great vids but come on

[@HaiChi_Kun]

Ikr? It is also happening for me. I need to do my damn hw! 😭😭😭

[@Tahairfanahmad]

Great video but you missed out on graphs of each

[@zhelyo_physics]

which graphs exactly? Let me know and I'd be happy to include them in future videos.

[@plty3931]

@@zhelyo_physicsgravitational field strength against radial displacement

[@husseinbasim5994]

3 ads in one video??

[@husseinbasim5994]

nevermind its 4 now!

[@randomuser12455]

man has to make money somehow

[@damodarramdoyal5890]

Hello, Newtons law of gravitation is GMm/r^2 not -GMm/r^2. 🤪

[@zhelyo_physics]

Well the magnitude is that, typically in most introductory courses they use the negative sign to show that it is produced by an attractive potential -GM/R. In further courses gravity is just treated as a scalar multiplied by a unit vector that indicates the direction. Hope this helps! : )

[@meer1288]

Chummun kk akz sa mo la