Planets DONT orbit around the centre of sun.

[911]

a1= F/m1 not F/a1 thats typo ...

@war&peace At what age this is taught in US?

 

[war&peace]

f

Yes if you go into technicalities like textbooks

That's why I called it a minor mistake but in fact it is a significant mistake as per textbooks and I used to explain the students about the importance of signs when dealing with vectors during my TA ship.

a1= F/m1 not F/a1 thats typo ...

@war&peace At what age this is taught in US?

Typo, In your post or mine?
I taught that part of vector analysis and intro mechanics at undergrad level..but that's the quick review. I think they teach this stuff in grade 7 or 8 but my schooling was not in USA, I came here for Bachelors.

 

[911]

That's why I called it a minor mistake but in fact it is a significant mistake as per textbooks and I used to explain the students about the importance of signs when dealing with vectors during my TA ship.

True.

Typo, In your post or mine?

My first post

I taught that part of vector analysis and intro mechanics at undergrad level..but that's the quick review. I think they teach this stuff in grade 7 or 8 but my schooling was not in USA, I came here for Bachelors.

Hmm...same here in India although its not repeated Bachelors

 

[war&peace]

True.


My first post

Hmm...same here in India although its not repeated Bachelors

In all top universities and even textbooks, first couple of chapters / lectures are always about the review of fundamentals since USA is an international destination for students and many students have different backgrounds, so an introduction is always done but a very condensed one so the details are skipped...that's done just to brush the memories.

 

[marbella]

Earth being round is also a lie many people say if earth was billion years old than today date will not be in early 2000 years it would be in 4 billion 100 million years today date

Totally agree, Brother.
N ya, 'woh kiya hai ' is my fav tv show too.

 

[war&peace]

Earth being round is also a lie many people say if earth was billion years old than today date will not be in early 2000 years it would be in 4 billion 100 million years today date

So you are saying the Earth is only 2000 yrs old?

Did you even hear about something called calendar and its start date?

Ever heard BC?

Ever heard that Prophet Abraham came around 4000 yrs ago?

The giant dinosaurs were killed 65 million years ago?

 

[dadeechi]

Riveting! Can you break it down further for a layman?

Let me try.

1) Let's say you have two marbles. One bigger, one smaller.

2) Now put the small marble on a table and give it a push and see what happens. Most likely it will roll in a straight line.

3) Now tie both the marbles with a thread. Now one end you have large marble and the other small marble.

4) Now hold the large marble in your hand and try to spin your hand. You would notice that the smaller marble at the end of the thread move in circular fashion.

5) Try to spin even faster and faster. There would be a time when the smaller marble at the other end might slip the knot and fly away from you

What did you learn? You applied some force in step 2 and the marble moved in a straight line which is the natural path. You applied some force on step 4 but this time it move in circular fashion as the hand is also applying reverse force through the thread. Now on step 5 the force was so huge that the smaller marble flies away in straight line.

Now if you replace these marbles with two magnets, you do not need a thread as the magnets are attracted to each other by nature.

Let say the smaller magnet is already moving but at the same time the bigger magnet is applying equal force on it so that it wont fly away or fall away and get attached to the bigger magnet. What would happen in this case is that as the bigger magnet is moving, the smaller magnet would keep moving around the bigger one.

Now if we put the bigger magnet is a bigger plastic ball and smaller magnet in a smaller plastic ball as an enclosure. The magnets within these balls still get attracted and now the smaller plastic ball goes around the bigger plastic ball. Now what we are saying is that it is not the plastic balls that are causing this circular motion due to attraction but it is due to the attraction of the magnets within those plastic balls.

The bigger plastic ball is Sun while the smaller plastic ball is Earth.

Hope I did not confuse you more....

 

[XenoEnsi-14]

I taught that part of vector analysis and intro mechanics at undergrad level..but that's the quick review. I think they teach this stuff in grade 7 or 8 but my schooling was not in USA, I came here for Bachelors.

Isn't that calculus? In 7 or 8th grade?! We are not Vulcans.

 

[war&peace]

Isn't that calculus? In 7 or 8th grade?! We are not Vulcans.

No it is not calculus...this is physics 101 : Newtons's laws of Motion, Conservations fields (Gravitational, magnetic,etc),
Force of gravity and acceleration due to it etc.. most of the relations / laws are expressed in Algebraic expressions. Though the complete descriptions of equations of motions involve differentials and integrals but that's taught at higher levels.
Said that, I used I think ( means I'm not sure) as I did not do my schooling in USA and I was taught this stuff in around those grades).

 

[XenoEnsi-14]

No it is not calculus...this is physics 101 : Newtons's laws of Motion, Conservations fields (Gravitational, magnetic,etc),
Force of gravity and acceleration due to it etc.. most of the relations / laws are expressed in Algebraic expressions. Though the complete descriptions of equations of motions involve differentials and integrals but that's taught at higher levels.
Said that, I used I think ( means I'm not sure) as I did not do my schooling in USA and I was taught this stuff in around those grades.

I don't remember ever being taught the actual formula, and math was my favorite subject. Oh well.

 

[Sneaker]

Yes, lala @Levina that's true claps for you

Basically, the Newton's laws of motion should also be interpreted like that

I have a question for pdfians and let's if any one can answer that correctl, I would be really surprised if any Indian will be able to give me the correct answer (especially the ones who did not study abroad), not to offend you but to instigate you enough to try to answer

Problem Description
Acc. to Newton's third law of motion, Every action has action that is equal in magnitude and opposite in direction, in customary mathematical notation

F_12 = - F_21​

Where F_12 and - F_21 are action and reaction of forces respectively.

So the question is an apple hanging on from the tree must exert the same amount of the forces on the Earth as the latter exerts on the former, then why Apple falls towards the earth but the Earth does not seem to rise towards the Apple...What is your explanation for this apparent anomaly ?

(Hint, Barycenter like explanation and the answer lies in classical Newtonian Mechanics and no need to resort to the theory of relativity or Quantum Mechanics)

Your example is flawed. I do understand what you are trying to say, but since apple is supported by earth (while it is hanging from tree), there is no question of earth moving towards apple (it is like sitting inside a car and pushing it). Now, the moment apple starts to fall down, then the situation you said arises. now, since g force is equal and opposite between the 2, with law of momentum (2nd law) f=m1a1=m2a2 (1 for apple, 2 for earth). a1/a2=m2/m1. assuming apple to be .1 kg, a1/a2=6e25 or acceleration of apple is 6e25 times of that of earth. so, technically, earth moves that much times the distance towards apple, meaning if apple was hanging 10 meter above earth (again some idealization required), earth will move 10/6e25/2*t^2 (too lazy to calculate t) towards apple...

It is still elliptical...the reason is the velocity(also momentum) at which earth was at the formation of our solar system was higher than the required velocity of a circular orbit.
Perfect circular orbits are nearly impossible in a natural system. Because the momentum has to be precise and there can be no other object around that could have any gravitational effect on any of the bodies.

Earth's orbit is near circular...

Its technicalities...nothing orbits around anything....everything orbits around a barycenter between that object and the other object it is supposed to be revolving around...a perfect revolution would require the barycenter to be exactly at the center of gravity of the bigger object.

I got that, my contention was planets still rotate around sun, just not centered around sun...

 

[war&peace]

Your example is flawed. I do understand what you are trying to say, but since apple is supported by earth (while it is hanging from tree), there is no question of earth moving towards apple (it is like sitting inside a car and pushing it). Now, the moment apple starts to fall down, then the situation you said arises. now, since g force is equal and opposite between the 2, with law of momentum (2nd law) f=m1a1=m2a2 (1 for apple, 2 for earth). a1/a2=m2/m1. assuming apple to be .1 kg, a1/a2=6e25 or acceleration of apple is 6e25 times of that of earth. so, technically, earth moves that much times the distance towards apple, meaning if apple was hanging 10 meter above earth (again some idealization required), earth will move 10/6e25/2*t^2 (too lazy to calculate t) towards apple...

Your comment is too late, a failed attempt to get over smart and impolite. Since the question has already been answered so your answer is needless and by plugging in numerical values you do not get authentic. At this level, we assume that the kids know how to calculate or rather how to use a calculator.

 

[Sneaker]

Your comment is too late, a failed attempt to get over smart, impolite, idiotic
Since the question has already been answered so your rant has no worth.

well now don't get edgy.. you were pointing at missed signs of some one, I just pointed out that your whole question is wrong.. but here is one for you, if a guy pushes a very heavy object (say earth), where is the reaction since neither of them move?

 

[war&peace]

well now don't get edgy.. you were pointing at missed signs of some one, I just pointed out that your whole question is wrong.. but here is one for you, if a guy pushes a very heavy object (say earth), where is the reaction since neither of them move?

You are not worth discussion so STFU and get lost.

 

[Sneaker]

You are not worth discussion so STFU and get lost.

ooops... teacher got some attitude...