Sir, you explained very beautifully. that show how great person you are. I really appreciate you taking time off from your busy life and teaching us these complex ideas and explaining them so easily. that even a dumb guy like me can understand. Bundle of Thanks.

You are a wonderful human being that the world is lucky to have. I wish you were my professor. *sigh*

I just can't believe, how talented teachers are there in this world. You made me your fan.

I’m a young guy and Im a big fan of astrophysics I loveeee videos about rockets and space thank you so much for this video🙂

Rocket Scientist you say? *scoffs* That's just conservation of momentum!

BEST PHYSICS LECTURES EVER !!!

Excellent explanation. We need more teachers and professors like this gentleman.

God level of teaching !

Prof i like how you teach physics, you actually teach physics whilst solving real world problems and i think that makes your lectures very cool.

This video is amazing. IT WAS EXACTLY WHAT I WAS LOOKING FOR to understand this concept. You really opened my mind about this concept. I love the way you teach, your interaction with students. Everything makes it so interesting. After this video i actually like physics more hehe.I wish you were my Professor.

THIS WAS SO GOOD

I like the explanation this is particularly good for revising something you have already learnt about

u r grt and i think very talented also.....thnx a lottt

Wow,u make physics so fun and practical.Teachers like u are what students need to fall in love with learning and physics.Grrreat video,pls keep up the good work :D :D

Your are a real genius nothing can compare u

Professor, Thanks a lot for this lucid explanation. My query is that, will this conservation of momentum hold true for a launch vehicle with in the earth’s atmosphere? Will it be correct to say that the stage separation of the rockets occur in order to reduce its mass as per the equation?

You are an amazing teacher Thanks a lot for these video's they are very helpful

what if the person throwing the wrench throws it using a battery powered wrench thrower and has a rope tied to the wrench, then after throwing, stops the wrench and slowly pulls it back to himself. When he has the wrench in his hands will the whole system have moved in an opposite direction of the throw?

Very nicely explained!

Thank you very much for this explanation

If you do reply my questioon is if something has a M=5kg which means 49N needed for thrust does how many times the needed N=there M/s like so does 147N mean it would go 2-3M/s 3if you account the needed intial force.

Does he write backwards?

What a great explanation thanx 😊

Thank you sir for your clear explanation

Sir ever amazing lecture regarding the same topic I got it very well

thanks, great explanation.

Its great .simply cleared .

Is the final momentum was additive in nature by considering the direction ? 1)P = mv +MV or 2)P = mv- MV Because some books consider 1st one for solving rocket equation.

Thank you so much Sir,I have an entrance exam for an amazing university coming up and I need ace it !!

Dr. A i have a question Does the gasses move with a velocity relative to the rocket???? if so Why?????

Thank you

Great explanation. Can we think of the empty rocket as the person and the wrench as the fuel?

Where do they write on?

Great explanation . Well done sir . But why is the Pf =MwVw-MpVp Isn't supposed to be + in between ?

I get the concept, but I struggle with grasping the practicality of this situation. If space is a vacuum, or there is no air and no pressure in space, what produces the opposite reaction to force your momentum in the opposite direction? Wouldn't the conservation of momentum in space force both you and the wrench to continue in the wrong direction? Or would the reaction between you and the wrench be enough?

Great explanation for the concepts presented but as a beginning physics student it leaves me wondering... At time 0, the astronaut and the ISS are orbiting the earth. When her tether breaks, the astronaut immediately throws the wrench. Assuming she throws it in a straight line from the release point, doesn't this propel her in a straight line back toward the ISS -- which will have moved on by the time she reaches its former position?

this is such a great video!! wonderfully explained. well done Alex.half of the time i was wondering what it was that you were writing on. :p

Ok. This means Law of conservation of momentum is same as Third law of motion. Right?

thanks

Beautiful example...

Great video, the class is really engaging, makes the student enjoy it. However, I have one question, Dr. Anderson. I apologize in advance for the lengthy message, but I think it’s necessary. I totally understand the conservation of momentum in situations like a person pushing another one on an ice ring; or an astronaut throwing a wrench in an attempt to get back to the ISS (by the way, if we had molecules of gases on space, we should be able to move just by kicking the air, because we would be exerting a force on the molecules, and the molecules on us, right? That's just a hypothetical situation). The thing is, I don't really understand the conservation of momentum when the system involves gases(explosions, propulsion of a rocket,etc). For example, if a have a big stone, stationary, then I put an explosive in a hole inside the stone. And let's assume that the stone breaks into 2 chunks, that gains momentum in a straight line only (the X-axis). Conservation of momentum says that the momentum applied by the gases at the chunk that moves to the right and at the one that moves to the left has the same magnitude but opposite direction. But how does that work? I mean, when I push someone on an ice ring, I apply a force on that person, and he/she on me, as a reaction. But how does that applies to gases of the explosive? Part of the gases apply a force to the chunk moving to the right, during a dt, which results in a quantity of momentum to the right(and the reaction force is the one that the chunk applies to the gases), and another part of the gases apply a force to the chunk that moves to the left, during a dt, which results in a momentum that has the exactly same magnitude of that momentum applied to the chunk that moves rightward, how crazy is that? I mean, am I thinking too much about it? I do not see my peers thinking this way(like, they do not talk about the gases of the explosive and etc) and it really frustrates me at times, because I am spending way more time than my peers studying this subject. Again, great class! Cheers from Brazil!

Conservation of momentum is valid when there is collision but.. What about rocket 🚀. One there is no collision between the particles exhausted out?

haha lets get it ! i love physics

“Decrease your mass to move faster”. Me: *shits myself during panic attack* that works 😅👍🏽 In practice, the ISS is experiencing circular motion, so unless you plan the maneuver proper, you could miss the station and start floating out into space. That said, this was a very instructive example!

What's that board on which u write called

Thanks

I love science, but seriously struggle with algebra... Yet every thing you just said made perfect sense straight away, I wish you could have been my science teacher👌

you're cool

I am not a degree holder but I can understand.

What are the odds! My names Alex!

You know Dr. Anderson. I love physics so much yet I do not understand even a single concept in it. I feel like my mind is blocked.

CLEARLY, gravity AND ELECTROMAGNETISM/energy are linked AND BALANCED opposites (ON BALANCE); as the stars AND PLANETS are POINTS in the night sky. Consider TIME (AND time dilation) ON BALANCE. By Frank DiMeglio

Is this also an example of Newton's third Law ?

where is rocket acceleration?????

but.. you could engage in some FLATULENCE and use that to Propel yourself toward the Space station!!.. lol, okay, that was Sophomoric but SOMEBODY had to say that!!.. (nevermind that I'm 65 years old and saying it... )

pretty sure a rocket is a heat engine of the internal combustion type, and thus dependent upon doing PV work. so i have no idea why you're blabbing about conservation of momentum and people throwing spanners in space.

Yes

Benedict Cumberbatch anyone?

All of the explanations of rocket propulsion I've seen on KZfaq invoke Newton's third law of motion or use conservation of momentum. The third law of motion states that if two bodies INTERACT then the force exerted by body A will be equal and opposite to the force body B exerts back on body A. It is incorrect to say that the gas exiting the rocket in the backward direction causes the rocket to move in the forward direction, by Newton's third law, because there is no INTERACTION between the exiting gas and the rocket. The law of conservation of momentum is not a law like Newton's second law of motion which states that if there is a net, non-zero force on a body then the body will accelerate in the direction of the net force and is always true. The law of conservation of momentum is derived from Newton's second law and is true only in certain restricted cases. If you have a system of interacting bodies, they must obey Newton's third law in pairs so that all the internal forces between the bodies add to zero. Second, the sum of the external forces acting on the bodies must also add to zero. If these two conditions are met, then the total momentum of the system of bodies will be conserved. A rocket leaving the surface of the Earth doesn't obey the conservation of momentum because gravity is an external force acting on the rocket. Only if the rocket is in outer space, far from any gravitating bodies, can the conservation of momentum be applied. So, how can you provide a simple explanation for rocket motion? I believe that all you need to say is that the hot gases entering the exhaust chamber of the rocket expand in all directions and that the part of the gas having a forward component of velocity pushes the rocket forward. It can be said that calculating the change in a rocket's velocity is difficult in a gravity field and conservation of momentum can be used in the simple case of no external forces.

Why not just use your SAFER device to propel yourself back to the ISS?