"It is terrible to do so but I have blocked out the sun" haha I love your videos you're awesome thanks! :)

@ppuckk

5 жыл бұрын

i heard he watered out the sun lol

@sherlockholmeslives.1605

3 жыл бұрын

This is far more intelligent than A-Level students! All the A-Level students I knew at school were thick!

My physics teacher is crap, so i have to teach it all to myself and this really helps, cheers man!

@rishadbari3177

3 жыл бұрын

Same bro, how did your exam go?

thank you for making physics less intimidating, i have you to thank for if i score well in my upcoming A levels :)

@DrPhysicsA

5 жыл бұрын

Celyn Tan Thanks. All good wishes for the exams.

Sometimes its the tumble dryer.

At 8:30 the gravitational potential energy is the work done to bring a mass m from infinity to a distance r from a mass M. That is obviously negative since PE reduces as you get closer to the mass M. But PE increases as you move away from the mass M.

if only there was a drchemistryA level

@yousseftarkhan9210

7 жыл бұрын

Did you find any ? I'm struggling to find one myself. I did for the record find a channel called allery chemistry but I didn't really watch it's videos yet.

@josephmurphy3298

7 жыл бұрын

Niket try a guy called E Rintoul

@haramboy6932

7 жыл бұрын

Thanks

@regisseng5483

7 жыл бұрын

Allery chemistry, clearly the best!

@AmbieWolfie

6 жыл бұрын

E Rintoul

what surprised me was you took the time to explain mv2/r. it was taught a long time ago to me and certainly I forgot and didn't understand this when I was watching you. Every aspect of your video revolve around the student and that is why this is so great, clear, engaging and easy to understand!

Washing machine in the background

@Sal-zi4tu

8 жыл бұрын

+John Fletcher or a work against gravity....

@jpanonymous892

8 жыл бұрын

+John Fletcher i kept thinking it was mine

@abeel.goraya

7 жыл бұрын

I thought it was a kettle

@meanqueen0024

6 жыл бұрын

There was also a cow....

@comic4relief

6 жыл бұрын

Abeel Goraya sounds like at around 6:00

You can choose your own convention for signs. The one I am using assumes that potential energy becomes zero at an infinite distance away. Since potential energy increases as you go further away that means it must be negative in order to increase to 0. But as long as your signs are consistent it doesn't really matter what convention you choose.

Sir you're the best! I wish there were more teachers like you.

Very well explained. Will check out your other vids. Thanks for uploading!

Force is a vector quantity. It has magnitude and direction. The negative sign is an indication that it is an attractive force (ie the force is in the opposite direction to increasing value of r). You don't have to include the minus sign as long as you remember which way the force operates.

Damn he provides a whole new perspective. Thanks sir.

A field doesn't do anything until you put something in. Like a temperature field that just sits there. Fields are capable of doing things, whether they do them or not. Put a block of ice in a temperature field and the ice melts. That's a brilliant start to the video! 🙌🏽🤯🔥🎊

I am delighted to hear it. Well done.

Excellent lessons. I am thrilled to have found these video lessons. Thank you. Thank you.

Thank you very much for this video. I honestly have learnt alot from this! Will be looking into more of your videos soon! :)

Awesome stuff, such a huge help! I love all your videos.

Sunny? In the UK?!

Good Luck on your IB physics exam tomorrow! I'm taking the same exam and I agree, these videos are indeed very helpful! Thanks DrPhysicsA! :)

It is the mass of the earth. The mass of the satellite cancels out at an earlier stage so does not feature in the equation here. Thanks for kind comment.

Thank you for your videos. They are reviving my interest in Physics from 50 years ago when passing the exam was more important than understanding what you are doing I am a bit confused about what is the difference between Gravitational Potential Energy (about 8:05) and the more conventional mgh kg m²/s² as you mention in your Electric Field Video comparing the two (at about 11:34) Substituting values for the variables they certainly don't agree. Many Thanks.

Calculate the force on the 3rd due to the first and then the second using F = GMm/r^2. Since the forces will be in opposite directions the net force is one minus the other.

i LOVE this, the explanation is good and easy understand.TQ so much ^^

Yes, from the centre of the earth to the centre of mass of the man. But I was ignoring the extra meter or so in 6400km.

Yep. Its a cuckoo clock with a cow instead of a cuckoo.

thank you very much i find your videos concise and extremely helpful !

you sir, deserve a medal! cheers

I take it you mean at 21:47 where I say r = 4.23 x 10**4 km. I haven't yet double checked it but could it be that you have calculated the value in m not km - in which case it would indeed be 4.23 x 10**7 m.

this channel is too good

Wow ! The best physics teacher ever ❤️

Thanks so much DrPhysicsA, your videos are so helpful! :)

There are so many books that I cant organise according to them all. I try to organise the videos in some logical order and hope the titles explain what they cover. I'm not sure what your Unit 4 OCR covers. Is it nuclear and particle physics? If so, there are videos on this in the A Level playlist - and more advanced videos on both in other playlists of mine.

This video really helped MR thanx!!

the vedio made me understand more stuff then i understood in the class so thank u sooo much

Thank you, your videos helped a lot! I take IB HL physics but the topics covered are nearly the same ( from the videos that I've watched) so it helps a lot.

These videos are so helpful!

such a wonderful explanation, thnqw

Great videos, thank you!

I learned the whole topic and more in 30 min than my school teacher who teaches us for a week and i learn 0 from him. Please make more.

Yes. If you think of the earth and the sun, the gravitational force from the earth to the sun is directed towards the sun whereas the distance vector from the sun is measured away from the sun. The key thing is not the minus sign but rather that you are consistent in your signing convention.

@paulebberson4884

4 жыл бұрын

The arrow on the Gravitational field line points towards the larger mass. Always.

6:42 - It sounds like there's a rocket preparing to launch.

Thank you so much! these are very useful!!

Love your videos!

Fantastic videos.

I may not have followed the point you are making. But if you square both sides then you will indeed get an expression without the square root. But then the left hand side will be T^2. Or have I missed the point?

ur video is really a good tool for revision thank u :)

Sir, it would be helpful if you could tell me where I can find the video on electric fields. Its not there in your classical mechanics playlist.

@user-hs3dg8jy3t

6 жыл бұрын

kzread.info/dash/bejne/eXh60raeltOqfag.html

Thank u v much for the content. Just one clarification though, If the total energy = KE + PE, when the object moves to infinite distance (r=infinity) both become KE=PE=0. However when r 0, Infinity and make it equals to (mv^2)/2, then I can get the same escape velocity. But still cannot understand what happened to all PE. If somebody can help me, really appreciated. Thanks.

This really helps. THank you so much

Amazing videos.

That's interesting... correct me if I'm wrong, professor, but considering that the centripetal force on the object is F=mv^2/r, does that not mean that the kinetic energy of a rotating body is F*r/2? That is an amazingly cool way to find that.

What is the speed falling from space to earth with a changing gravity strength. Do you do a video about this?

Hi sir woaaahh just wowwww i really love physics and you have deepen it

WE NEED YOU PLEASE COMEBACK, IT VERY USEFULL IN PANDEMIC (2022)

This was posted 10 years ago but my God you are good....

Thankyou So much SIr you explained really in great manner :)

Thank you so much. This video is very useful for me :)

I assume you are referring to the section starting at about 11:23. You are right in all you say except "small v is the length". This is a vector diagram so v is velocity not length. See my video on adding and subtracting vectors for tail to tail subtraction of vectors. So v on both sides of the equation is velocity.

Ur video rocks Very helpful

What a great teacher you are. Thank you for your videos. Could you make one describing the simple two bodies system and the equation that follows ?

@DrPhysicsA

10 жыл бұрын

There is a video in the A-level playlist which looks at momentum in two dimensions.

@NicolasGreg

10 жыл бұрын

DrPhysicsA Thank you for the reply. An interesting video indeed. But in fact i was thinking of the two bodies problem in the planetary context. I have read something with a reduced mass to write the exact equation of the movement of a satellite which ends with this r = K²/(GMt( 1 + e cos θ )). I didn't understood how to arrive to this result. I was hoping you could shine some lights. (Sorry for poor english)

I was in year 6 when this was filmed...

great video, very clear and engaging. Thank you sir.

@xubarney1326

Жыл бұрын

as well as logical

Thank you, It was very helpful.

I had the same issue. If you square the whole expression, (2 x pi x r) / v, while substituting the root GM/r for the v, you get the expression you derived without the square root in the expression...

Drops lid whilst talking *oops* continues btw thanks so much for these videos, it has helped me understand mechanics a lot better than how my teacher explained it.

Thank you so much.

Do you have a video on the gravitational potential graphs etc. please?

For escape velocity, assuming a conservative system where we end up with the kinetic and potential energy of the system as: K_f + Ep_f = K_i + Ep_i, where sub 'f' is final and sub 'i' is initial, should we not set up the equation where the left side is 0. The final kinetic energy and the potential at infinity would be zero. That leaves us with 0 = 1/2mV^2 -- GMm/r. This rids the (--) as shown in 26:31 when we rearrange to get 1/2mV^2 = GMm/r.

Thanks for the derivation of T.

At 21:13- Period of geostationary, orbiting body: one sidereal day, 86,164 seconds.

Hello sir. Very nice presentation.

in my book says ' the magnitude of minimal velocity of a rocket in order for the rocket to be able to escape from grabity is = square root of 2g× m over r. is that correct ?. there was one similar except it doesnt have a square root

The minus sign is there as gravitational force is attractive. I get the distance in the opposite direction of the force, however that will just confuse students (why cant they measure from bottom to top etc.)

yh sure my teacher is a no brainer, n wif vidz lyk thez lyfz made a lot easier......................anks a lot man, u da best

I really like the proof of centripetal acceleration= vsquared over r Ive never seen it because most teachers don't explain why that is

Question: In the video, you say velocity, v, is a vector, but then you say it's speed at 12:32. How do you convert a vector to a single variable like that?

Thanks! Unfortunately though, CIE tends to ask why there is a negative sign, and they don't accept the direction argument.

technically gravity is just the result of the curvature of the fabric of space time and is not a pulling force. a large mass would curve or distort the space around it like rubber sheet being distorted by say a bowling ball. essentially other masses would "roll" towards the center of the distortion (like a marble rolling down the curve in the rubber sheet we talked about earlier made by the bowling ball). so gravity is not a "pull" but a "push. still like your calculations

No I am only squaring 2 pi r so I can put it inside the square root.

Thanks a lot!!!

you have helped a lot over the past few weeks of revision for me. got my first A2 exam in just under an hour. I will let you know how it goes in a couple of months time. (predicted A, although will be happy with a C). Fingers crossed I guess!

@DrPhysicsA

6 жыл бұрын

Dan Hyde good luck. Hope it goes well.

@zarishahmed9356

5 жыл бұрын

I wonder if it went well.

@danhyde7501

5 жыл бұрын

Zarish Ahmed got a B so I was super happy. Completely forgot about that comment.

yo man got a B in physics, and i thought id thank you if i did cuz i swear to god i didnot know a word 3 days before the exam. i actually had to the buy the text book then cuz id lost mine, your videos saved me. thankyou very much

Thanks so much. :)

15:26 Moooo!

Really? I struggle to see why. G is a constant. M and m are both scalars. F and r are the only vectors in the equation. And F is in the opposite direction to r. It may be they want you to say that Force is the differential of potential energy and PE is always negative (because it increases as you go further away from the earth and is 0 at infinity)

Sir, i have a question about squaring both sides at @18:25.. how did u divide the square root of r/GM with 2 pi r ? Pls. explain

@DrPhysicsA

10 жыл бұрын

All I have done is to take the 2 pi r into the square root. In order to to do that I had to square it first so that when you take the square root you get back to where you started.

@danny10846

10 жыл бұрын

DrPhysicsA I instead substituted v = 2 pi r / T straight into the equation and then rearranged for T^2 after squaring both sides. Thanks for the great video by the way :)

if you listen very closely you can hear your brain frying

@ibrahimgamingbro783

6 жыл бұрын

You need glasses.

Good Day Sir, could you Show us how to calculate gravitational Potential energy at earth center?.... Thank you.... 👍👍... Very well explained Video Sir

Two weeks before midterm Statics & Dynamics exams my British professor said that we could skip the next week's classes to study for the exam, but suggested that we show up anyway because he would "revise everything we have learned thus far". I almost passed out... in American usage 'revise' means 'change what was previously looked at', so it sounded like he was tossing out everything we had previously studied and replacing it with something else.

At 21:00 is M the mass of the earth or of the satellite? Thank you, very helpful

Great videos! P.S. Your voice reminds me of Mark Halliley (The Apprentice Narrator).

Thank you sir ❤🌑

Hey can someone how he got the m/s^2 from the other Equation?

please make a video on example exam style questions

thin you for this explanation,doctor,but i have a question,in this forumla ,you h'avent considered ,,,the earth mouves in orbit of the sun,this mouves infulences ,the satelite mouves ,why can you expain this in the formula,frendly

This guy is adorable!

In the first diagram you arrived at dᶱ = dx / r = vdt/r where r = radius and v is velocity In the second vector diagram You arrived at dV / v = dᶱ where dV= change in velocity and small v is the length When you equated dᶱ in both the equations dV/v = vdt/r where left hand side denominator v is length and right hand side numerator v is velocity And you have multiplied the length v lhs with velocity v rhs and arrived at v2 /r = dv/dt Could you please clarify or am I missing something. Thanks

So helpful

Yes, that's what I did *headdesk* thankyou very much.