Problem 211 It's all about the Moon

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Lectures by Walter Lewin. They will make you ♥ Physics.

Күн бұрын

Пікірлер: 78

@noobisaures 2 ай бұрын

a) 1.68 km/s (orbital velocity of moon) b) 1.8 hrs c) elliptical d) unbound hyperbolic

@capichow 2 ай бұрын

Thanks for saving me years time traveller ♾️🖖🏼🙏🏼🫡🏡❤️♾️🏆

@rafaelpadilla757 2 ай бұрын

a) v_orbital=sqrt(GM/R)=1.68 km/s b) T=2πR/v_orbital=1.8 hours c) v_escape=sqrt(2)·v_orbital=2.55 km/s. Thus, with 2 km/s the orbit is a elipse. d) 3 km/s is greater than v_escape so it goes to infinity in a hyperboloidal fashion.

@capichow 2 ай бұрын

It may take many years for me to answer this question But I have the answer for the falling tree you posted years ago 😂 MAGNUS EFFECT

@Allmix551 2 ай бұрын

Sir moon has on atmosphere because (r. m. s velocity )of all the gases is more than escape velocity from it's surface . He's right.

@surendrakverma555 2 ай бұрын

Thanks Sir for posting an interesting problem.

@ManoharLal-gv2jy 2 ай бұрын

Sir please take rest you seem very tired by your voice

@mqx133 2 ай бұрын

Hello! Greetings from Caucasus.

@ShahinDiganaev 2 ай бұрын

Hi im also caucasian

@foxhound1008 2 ай бұрын

Orbital velocity at surface of moon = 1.684 Km/s Time to orbit = 1.8 hrs Escape velocity = 2.38 Km/s Speed of 2.0 Km/s would result in an elliptical orbit Speed of 3.0 Km/s would result in a hyperbolic orbit as it would arrive at infinity with energy with kinetic energy remaining.

@oldtvnut 2 ай бұрын

I always forget the formula for centrifugal force, so I work it out by considering for circular motion using: x = Rcos(w) x' = velocity = Rwsin(w) x'' = -a = -R(w^2)cos(w) = -(MG)/(r^2) = 1.626 m/s^2 From these calculate w and v. Part a: v = 1680 m/s Part b: from w, calulate T = 6494 s = 1.8 hours Part c: escape velocity is sqrt(2) x circular velocity (did not derive this formula, found it on the internet) = 2377 m/s. Therefore at 2 km/s, orbit is elliptical, and Part d: at 3 km/s, orbit is hyperbola (satellite escapes)

@080allanthomas5 2 ай бұрын

1. Critical Velocity = 1.684 km/ sec 2. Time Period of Satellite = 108.27 minutes 3. Elliptical orbit (Since Given velocity < Escape Velocity) Escape Velocity of Moon = 2.375 km/ sec 4. Hyperbola. Since Given velocity > Escape Velocity.

@gauri-s07 2 ай бұрын

Thank you so much sir!

@rashishsaini50 2 ай бұрын

a) 1683.7 m/sec b) 6478.8 sec = 107.9 minutes c) ellipse d) Hyperbola

@apurvkumar8223 2 ай бұрын

Its an easy problem however I forgot the formulas I used to solve it. However I know how to get it. Supposing the moon has a perfectly round shape then a satellite in orbit will be in constant accerleration as it velocity is constantly changing thus it is going to face two kinds of force a centrifugal force and force due to gravity so we have the equation mv^2/r=GM/r^2 from here we will get velocity. after getting the velocity we can easily get the time it takes to take one complete orbit by solving 2*pi*r/v.. now if the velocity is more than the velocity we get at that value of 'r' then the orbit will be elliptical and the apoapsis will be just on the opposite side. if the velocity is less than what we get then the projectile is at apoapsis. I also would like to add one more thing on why the moon has to be round.. This is because the gravitational field will be uniform in 3D space. Only then the projectile will be able to stay in orbit as predicted otherwise it may loose its orbit. Another fact that we can visualise it as the satellite is in freefall it just happens that when it falls lets say 1m in downward direction it simultaneously gains 1m due to high speed and the spherical surface of the moon. Thankyou professor lots of love

@ArturoHernandez-y3k 2 ай бұрын

a) 1680.49m/s b)6.494 s c)elliptical d)hyperbolic

@rashishsaini50 2 ай бұрын

hell yeah this problem seems fun to do

@Anurag-qo2kz 2 ай бұрын

Hi sir! I just love you! You are the best

@FerzanTapramaz 2 ай бұрын

a) 1.68 km/s. b) 108 min. c) a parabola. d) one arm of a hyperbola.

@YannisAlepidis 2 ай бұрын

a) 1680 m/s b) 1.8 h c) ellipse d) hyperbola. The sattelite escapes from the moon's gravity field.

@ashwin8839 2 ай бұрын

Sir a doubt! An engine pumps water through a hose pipe. Water passes through the pipe and leave with a velocity 2 m/s. The mass per unit length of water in pipe is 100 kg/m. What is the power of the engine ? Here in the question if we use P = W/t, we get 400W and when use P = FV we get 800 W so which should be the correct answer to this question sir.

@carultch 2 ай бұрын

Set up the Bernoulli equation for idealized liquid flow: P1/rho + v1^2/2 + g*z1 + W_dot_in/m_dot = P2/rho + v2^2/2 + g*z2 For your example, both pressures are equal, and both elevations are equal, so we can strike those two terms. v1^2/2 + W_dot_in/m_dot = v2^2/2 Assume v1 is negligible. Solve for W_dot_in: W_dot_in = m_dot*v2^2/2 m_dot = 100 kg/m * 2 m/s = 200 kg/s W_dot_in = 200 kg/s * (2 m/s)^2/2 W_dot_in = 400 Watts The reason why "P=F*V" is not valid, is that velocity is not constant during the process of accelerating the water from rest. If you account for its continuous speed-up from rest, you get the 1/2 factor in the kinetic energy formula that needs to apply in this context.

@ashwin8839 2 ай бұрын

@@carultchThankyou for your reply..

@ayanokojikun1st 2 ай бұрын

Hii sir Big fan from india

@srisaran-l3y 2 ай бұрын

Sir I have an idea about Black Hole and White Hole :- which is a single black hole that has a connection of multiple white holes. We can't observe till now white holes until now because of multiple connections of white holes with a single BLACK HOLE. So, more number of white holes sucking a particle and the particle is destroyed before coming out. White holes are not white they are invisible (light is destroyed before coming out ).Hence , we can't observe it . SIR REQUESTING YOU TO REPLY TO THIS TEXT AND I LIKE DEVELOP THIS WITH YOU SIR

@lecturesbywalterlewin.they9259 2 ай бұрын

google "white holes" and google "black holes"

@ShreyanshChaturvedi07 2 ай бұрын

(A) The speed at which the satellite must be shot out from the gun is approximately 1680.49 m/s 1680.49m/s. (B) The time it takes the satellite to go once around the Moon is approximately 6494.46 seconds 6494.46seconds, or about 1.80 hours 1.80hours.

@darkomalic5950 2 ай бұрын

a) The speed with which the satelite must be launched is 1680 m/s. b) The time that it takes for this satelite to go around the Moon is 1h 48 min (1.8h) c) The orbit will be an ellipse with the following parameters: semimajor axis 2a = 6000km; this satellite s periapsis (if we can call it that) is exactly equal to R = 1737km, that is, it is exactly at the moon surface at its point nearest to the Moon. Its apoapsis is at the distance 2a - R = 4263 km, that is, it is 2526 km away from the Moon's surface at its farthes point in orbit. It is interesting to notice that in the same orbit the satellite can at one point be nearly at the surface of the Moon, and at the other point 2500 km away. The time it takes for this satellite to go around is about 4h. d) This orbit will be unbound because the satellite was given a higher speed than the escape velocity at launch, which equals 2376 m/s. Given that the launch speed was 3000 m/s, the satellite goes out to infinity and it reaches it with a finite speed.

2 ай бұрын

Things that escape their planets usually end up hitting another planet or star, possibly the Earth or the Sun.

@GamingPro69420 2 ай бұрын

Sir my question is what does the first law of Newton state?

@lecturesbywalterlewin.they9259 2 ай бұрын

2+2 = 5

@Ashu_x_pandit 2 ай бұрын

@@lecturesbywalterlewin.they9259😂😂😊

@harshwardhansingh-j8i 2 ай бұрын

😂@@lecturesbywalterlewin.they9259

@Anirudh.__900 2 ай бұрын

@@lecturesbywalterlewin.they9259😂😂😂😂😂😂😂...sir you are awesome ❤

@dhanalakshmikasimani9397 2 ай бұрын

@louderthanbombz 2 ай бұрын

Thank you sir this helped alot❤🙏

@lecturesbywalterlewin.they9259 2 ай бұрын

Glad it helped

@louderthanbombz 2 ай бұрын

@@lecturesbywalterlewin.they9259 ❤️🥹🙏

@chinmoydeka2719 2 ай бұрын

Hello sir had some doubt regarding quantum mechanics Recently i also tried to mail you but it wasnt delivered to you thats why im here. And my doubt is whenever we observe electrons from the same frame of reference we found that it follows Heisenberg uncertainty principal and therefore we can't determine position and momentum simultaneously but what happens if we observe electrons from a different frame of reference in which time is relatively slow for us or we observe the electron for which time is slower then how electron behaves.. And what happens if we observe a particle by a diffracting slit.. And the next question is we observe an electron from a different medium in this case we observe electrons from the same frame of reference but from different mediums. And let suppose the observer is in the denser medium and the electron particle in the rare medium and travels from right to left. For us the speed of light is slow and because of this I don't know if it is right but I think we see the particle as a sort of waves of smaller wavelength moving from left to right like a small or light and because of that if we find some equation of that case then probably we can get some probability of finding electrons because we see the things slower but because of that time dilation and length contraction will happen but if we can find some sort of equation then we can also put some counter values to counter the time dilation and length contraction like a constant. And we can also put gravity in action by which the mass of the electron will rise and we can observe it more precisely.. I don't know if you understand the question because I'm not able to explain my question properly But please give me some way to research it better. So please guide me anyway so that i can study it better chinmoy17deka@gmail.com that's my mail id... Please give me some idea

@lecturesbywalterlewin.they9259 2 ай бұрын

take QM courses - MIT's 8.04 and 8.05 are both on my channel.

@CricSpinOfficial 2 ай бұрын

hats off to you sir ❤

@ulfhaller6818 2 ай бұрын

G = 6.674 × 10-11 m3kg-1s-2 M = 7.35×10²² kg R = 1737 km = 1.737×10⁶ m a) Orbital speed: Centripetal force = Gravitational force => mv²/r = GMm/r² => v = √(GM/r) r = R => v_orb = √(GM/R) ≈ 1.68 km/s b) Length of the orbit = 2πR => T = 2πR/v_orb ≈ 2π×1737/1.68 => T ≈ 6490 s ≈ 108 min ≈ 1.8 hours Escape velocity: K = kinetic energy U = gravitational potential energy. Total energy is conserved. Initial energy: Kᵢ = ½ mv² and Uᵢ = -GMm/R Final energy: At infinity v -> 0 and U -> 0 => total final energy -> 0 => ½ mv²- GMm/R = 0 v_esc = √(2GM/R) ≈ 2.38 km/s c) v_orb < 2.00 km/s < v_esc This means that the satellite will make an elliptical orbit around the Moon. d) 3.00 km/s > v_esc This means that the satellite will leave the Moon in a hyperbolic trajectory.

@learningwithjojok5137 2 ай бұрын

7 august my birthday that's why I forgot all lecturer after that's 😢

@samuel__777 2 ай бұрын

❤

@rexanne5227 2 ай бұрын

Sir , Does that actually work... Like you said eat yoghurt and all those stuff to master Physics. The thing is i don't like Yoghurt so is there any other tip😅

@lecturesbywalterlewin.they9259 2 ай бұрын

there is no other tip that is as powerful as eating yogurt every day but *never on Fridays* It also worked for Einstein

@rexanne5227 2 ай бұрын

@@lecturesbywalterlewin.they9259 Alright 🥲

@MasumAhmed-io5fm 2 ай бұрын

Sir please suggest a good chemistry teacher in your knoledge . Please sir we face lot of problems with chemistry .

@carultch 2 ай бұрын

I'll endorse Professor Dave Explains.

@VIOLET-po2vd 2 ай бұрын

✨✨✨✨

@ShreyanshChaturvedi07 2 ай бұрын

as a school student I tried my best to solve the question and was able to do a and b only ....... please let me know whether i am correct or not ?

@nagasaranyanakka5507 2 ай бұрын

Professor walter are you MITAN 😊

@منوبيالفلسطي 2 ай бұрын

Dear Professor Walter The older a person gets, the closer he gets to the grave..sorry ! but this is a truth I personally appreciate your knowledge of physics.. You are a true brilliant physicist, I testify to that, but you do not want to understand that the orderliness of the universe and fine tuning in it = is one of the greatest conclusive proofs of the wise Creator. Neither physics nor any experimental science will be able to answer the question of purpose coz it's out of its scope.. and life in the absence of this answer is literally hell no matter how much a person persists and tries to convince himself that he is happy My last advice to you / Convert to Islam and allow your mind and heart to see the full picture.., And only then will you taste the "meaning" of life and be born again..I swear!, and death will not frighten you because you will realize that this is just a temporary station in which we were put for test, and after that is the station of the afterlife that never ends! I recommend that you watch debates between Muslims and atheists This is fair because you will see the arguments of both teams for yourself and judge ! Best Wishes

@lecturesbywalterlewin.they9259 2 ай бұрын

I respect what you believe in - I expect that you too respect what I believe in - I am an atheist - plse make no attempt to convert me to Islam I will also make no attempt to convert you to atheism. *Freedom of religion is a corner stone to all democartic societies.*

@x0ziil 2 ай бұрын

💩💩@@lecturesbywalterlewin.they9259

@HarshMishra-sf6ec 2 ай бұрын

Sir please solve jee main and advanced question its a humble request love from India ❤❤❤❤

@lecturesbywalterlewin.they9259 2 ай бұрын

I do not solve problems for viewers. I teach Physics - There are 1400 videos on my channel which are all at your disposal (incuding my 94 MIT course lectures 8.01, 8.02 and 8.03)

@riyadas421 2 ай бұрын

Is there any book of Walter Lewin?

@lecturesbywalterlewin.they9259 2 ай бұрын

For the Love of Physics

@aayoushsinghthakuri7 2 ай бұрын

Hello Walter lewin sir , I like the physics most but I am in 10 th class now so , I am not able to give more Time in physics . But I love physics too much ❤ # my fav #alakh sir # Walter lewin sir # Hc Verma . Love from NEPAL ❤ !

@gaurava4883 2 ай бұрын

Yes im first. and will be the first one to learn :) although im taking business i still love to go through your videos!

@uni0590 2 ай бұрын

Sir my question is Does worm holes exist in the universe and also multiverse ?

@lecturesbywalterlewin.they9259 2 ай бұрын

use google

@shivamrajRMS 2 ай бұрын

@@lecturesbywalterlewin.they9259Good morning walter sir Sir. I am in 10th class and I want to join the Indian armed forces because I am passionate for it, after that I will love to develop an ecosystem which will pull students out of the trap of iit, neet and government jobs. So that they could do something meaningful for this nation. Sir in this race of government jobs we have no CV Raman left but we have you. Please guide me.. I am not of any worth for you but I will always wait for your reply.