# Search results

1. ### Can subatomic particles be PROVED to exist?

I just love philosophy. So if you (and the mentors) never mind for this occasion... I guess I can't deny my existence. Cause the moment I deny it is actually the moment I accept it for proving the existence of my denial. So I exist. ["I think, therefore I am." - Rene Dascartes] Okey I admit this...
2. ### A question on Dimensional analysis

Thanks. So I conclude - dimensional analysis works for equations; but it will work for proportionality only if the constant is unit less. (The book was a bit confusing.)
3. ### A question on Dimensional analysis

It never seems to be the case. Serway's book describes it as a general procedure. Here is the excerpt from Serway's book:(as this page can be previewed in amazon; I think it never breaks any copyright) Now this certainly works for x ∞ (a^n)(t^m); but what happens when we apply this for...
4. ### A question on Dimensional analysis

Wait, I have another question. In law of gravitation we know F = GmM/r^2 Here G is a proportionality constant, isn't it? Then how come it is not a pure number (ie it has units like) 6.67×10^−11 N·(m/kg)2 ?
5. ### A question on Dimensional analysis

OOPPss... Suddenly I understand. k is not anything like length mass or time, right? Maybe thats the reason why they left out k?
6. ### A question on Dimensional analysis

This is actually an example from Physics for Scientists and Engineers by Serway. I am confused about the way they solved it. Homework Statement Suppose we are told that acceleration a of a particle moving with uniform speed v in a circle of radius r is proportional to some power of r, say...
7. ### Concept of Free Fall in question!

As Nugatory said, objects of different masses feel different gravitational force. Now, I think your confusion is, if masses feel different magnitudes of gravitational force how come they accelerate at same rate? Right? In other words you are asking if F is different how can g be same? You...
8. ### Wool vs Cotton - electronegativity?

For both reasons; I think. Cotton is more electronegative (then wool) implies Cotton atoms' (outer shell) electrons are more tightly held than wool. Wool is less electronegative (then cotton) implies Wool atoms' (outer shell) electrons are more loosely held than cotton.
9. ### Is Time a vector quantity?

I think I got the idea. Thanks everyone.
10. ### Is Time a vector quantity?

That post clarifies a lot.
11. ### Is Time a vector quantity?

Well, well... I think I should take a break. :-)
12. ### Is Time a vector quantity?

Hey, thanks a lot. :-) But I wonder why while writing intro physics books they never clarify this. I started this thread just for kicks but in the end I have learned something important.
13. ### Is Time a vector quantity?

Sorry, but I dont understand this. For example: the unit vector along x axis is a 1D vector. Did you mean to say that its actually a scalar? And also,
14. ### Is Time a vector quantity?

I am beginner intro physics student. So I might be lacking in concept. That said; when we study 1D kinematics don't we consider 1D quantity like 1D velocity. 1D acceleration as vectors?
15. ### Is Time a vector quantity?

If we multiply velocity with time, we get displacement. How can we multiply two vector and get a vector? (I thought it is possible only under cross multiplication, but you reminded me that cross multiplication is only for 3D.) So how do we multiply the 'vector' time with any other vector...
16. ### Is Time a vector quantity?

how to multiply then? Hmm, so time IS a vector. But what happens when we multiply time with a vector quantity like velocity? Will it be a cross or dot? (cross maybe? because displacement is a vector...) And what will be the angle between? I am confused.
17. ### Is Time a vector quantity?

Ok I am not serious here. I was just wondering - as for us, time always moves forward; doesn't that mean time have a direction? So why not call it a vector? :-)

Thank you.
19. ### Centripetal vs Radial acceleration

I am reading introductory physics from Serway. Where they say if a_r is radial acceleration and a_c is centripetal acceleration then a_c = v^2/r and a_r = -a_c = - v^2/r But aren't the radial and centripetal acceleration same (correct me if I am wrong)? Why is there a minus sign? The...
20. ### A basic question about free fall (concerning Galileo and Aristotle)

Firstly, do you agree that the (above stated) logical inconsistency of Aristotle shown by Galileo is sound? (Which is my original question.) Secondly, I understand the importance of experiment in science. But if we can easily show that a theory is logically inconsistent then can't we stop and...
21. ### A basic question about free fall (concerning Galileo and Aristotle)

I can't find what is wrong with Galileo's reasoning. And I wonder why an experiment was necessary to prove Aristotle wrong?
22. ### A basic question about free fall (concerning Galileo and Aristotle)

I really cant think my way out of this.
23. ### A basic question about free fall (concerning Galileo and Aristotle)

This question is from Resnick, Halliday, Krane; Physics 5th edition. This is not actually a homework problem rather a question and so I hope it's not inappropriate to post it here. If m is a light stone and M is a heavy one, according to Aristotle M should fall fall faster than m. Galileo...
24. ### A storage problem

If universe is a thing, then it must stored somewhere - ie may be in a superior universe. So if you think like this, it wont end. Now if we think storage is endless, that may be a kind of thought, I agree. But it isnt clear enough. We need to have an idea of the last storage. And surely the...
25. ### A storage problem

Take it a bit differently. A program is stored in a hardware. A hardware in a Computer. A computer in a room... house... city... country... earth... thus ultimately we reach to Universe. So everything is stored in the universe. What is universe? We can take a piece of wood and say, this is a...