The Naked Scientists

The Naked Scientists Forum

Author Topic: Physics Question of the Week  (Read 10877 times)

Offline Mjhavok

  • Sr. Member
  • ****
  • Posts: 468
    • View Profile
    • http://cantmakeadifference.blogspot.com
Physics Question of the Week
« on: 13/08/2006 21:53:21 »
Suppose that the nucleus of an oxygen atom, which has 8 protons and usually has 8 neutrons, were split exactly in two. What element would be the result? How many atoms of this element would there be? Neglect, for simplicitym any energy that might be involved in the reaction.


-Steven

In a time of universal deceit - telling the truth is a revolutionary act.


 

Offline lightarrow

  • Neilep Level Member
  • ******
  • Posts: 4586
  • Thanked: 7 times
    • View Profile
Re: Physics Question of the Week
« Reply #1 on: 15/08/2006 17:01:51 »
Helium(4) isotope: 2 protons and 2 neutrons.
 

Offline Mjhavok

  • Sr. Member
  • ****
  • Posts: 468
    • View Profile
    • http://cantmakeadifference.blogspot.com
Re: Physics Question of the Week
« Reply #2 on: 15/08/2006 18:29:30 »
No
 

another_someone

  • Guest
Re: Physics Question of the Week
« Reply #3 on: 15/08/2006 23:29:28 »
It doesn't take much to divide 8 by 2, look up atomic number 4 on a periodic table, and come back with the answer Beryllium.



George
 

Offline Mjhavok

  • Sr. Member
  • ****
  • Posts: 468
    • View Profile
    • http://cantmakeadifference.blogspot.com
Re: Physics Question of the Week
« Reply #4 on: 16/08/2006 00:36:08 »
Hehe yep. It makes a rare isotope of beryllium. It turns out that the most common isotope of beryllium has five neutrons in its nucleus.
 

Offline Mjhavok

  • Sr. Member
  • ****
  • Posts: 468
    • View Profile
    • http://cantmakeadifference.blogspot.com
Re: Physics Question of the Week
« Reply #5 on: 16/08/2006 00:38:54 »
Physics Question of the Week

What is the critical angle for light rays shining upward from beneath a fresh water pond?

-Steven
 

another_someone

  • Guest
Re: Physics Question of the Week
« Reply #6 on: 16/08/2006 00:49:08 »
You didn't expect me to know this off the top of my head did you?  Unfortunately, google all too easily replies that the critical angle to an air/water interface is 48.6 degrees (although this must depend upon purity of the medium, temperature and pressure of the medium, and even the colour of the light).



George
 

Offline lightarrow

  • Neilep Level Member
  • ******
  • Posts: 4586
  • Thanked: 7 times
    • View Profile
Re: Physics Question of the Week
« Reply #7 on: 16/08/2006 11:47:26 »
quote:
Originally posted by another_someone

It doesn't take much to divide 8 by 2, look up atomic number 4 on a periodic table, and come back with the answer Beryllium.



George



Right. My mistake. I'm sorry.
 

Offline lightarrow

  • Neilep Level Member
  • ******
  • Posts: 4586
  • Thanked: 7 times
    • View Profile
Re: Physics Question of the Week
« Reply #8 on: 16/08/2006 12:16:53 »
quote:
Originally posted by Mjhavok

Physics Question of the Week

What is the critical angle for light rays shining upward from beneath a fresh water pond?

-Steven



SIN(i)/SIN(r) = 1/n(H2O); n(H2O) = 1.336 at 550 nm (according to http://www.philiplaven.com/p20.html); r = 90° --> i = 48.48°. In the entire visible spectrum it varies from about 48.1° (violet) to 48.7° (red).
« Last Edit: 16/08/2006 16:33:07 by lightarrow »
 

Offline Mjhavok

  • Sr. Member
  • ****
  • Posts: 468
    • View Profile
    • http://cantmakeadifference.blogspot.com
Re: Physics Question of the Week
« Reply #9 on: 16/08/2006 22:29:38 »
Answer is 48.8°

Given that the angle in this situation is defined with respect to the normal to the surface, not with respect to the plane of the surface.

I didn't give enough variables to allow you to be more accurate. 48.7 and 48.6 are close enough.

Well done.

 

Offline Mjhavok

  • Sr. Member
  • ****
  • Posts: 468
    • View Profile
    • http://cantmakeadifference.blogspot.com
Re: Physics Question of the Week
« Reply #10 on: 16/08/2006 22:32:15 »
PHYSICS QUESTION OF THE DAY (IT SEEMS LOL)

The geomagnetic field is produced by what?


Steven
_______________________________________________________________
In a time of universal deceit - telling the truth is a revolutionary act.
« Last Edit: 23/08/2006 23:28:36 by Mjhavok »
 

Offline syhprum

  • Neilep Level Member
  • ******
  • Posts: 3813
  • Thanked: 19 times
    • View Profile
Re: Physics Question of the Week
« Reply #11 on: 24/08/2006 12:11:20 »
The movement of a condutive fluid (probably Iron) relative to the rtation of the earth in a layer immediatly above the earths solid core.

syhprum
 

Offline lightarrow

  • Neilep Level Member
  • ******
  • Posts: 4586
  • Thanked: 7 times
    • View Profile
Re: Physics Question of the Week
« Reply #12 on: 24/08/2006 12:54:41 »
quote:
Originally posted by syhprum

The movement of a condutive fluid (probably Iron) relative to the rtation of the earth in a layer immediatly above the earths solid core.


Just to Add: this movement happens in the presence of a magnetic field, and this produces an electric current, that, in turns, produces a magnetic field that reinforces the first, regenerating it (Dynamo theory).
How this can happen is however still a mistery for me, because, usually, an induced magnetic field is opposite to the first one (inducer).

The first (igniting) magnetic field could have been, for example, the one of another planetary object near the earth millions of years ago.
 

Offline syhprum

  • Neilep Level Member
  • ******
  • Posts: 3813
  • Thanked: 19 times
    • View Profile
Re: Physics Question of the Week
« Reply #13 on: 24/08/2006 19:03:05 »
It is well established that the earth early in its history was in collision with a mars sized object (Mars?) that lead to the creation of our moon, could this be the seed of the magnetic field?

syhprum
 

Offline syhprum

  • Neilep Level Member
  • ******
  • Posts: 3813
  • Thanked: 19 times
    • View Profile
Re: Physics Question of the Week
« Reply #14 on: 24/08/2006 12:11:20 »
The movement of a condutive fluid (probably Iron) relative to the rtation of the earth in a layer immediatly above the earths solid core.

syhprum
 

Offline lightarrow

  • Neilep Level Member
  • ******
  • Posts: 4586
  • Thanked: 7 times
    • View Profile
Re: Physics Question of the Week
« Reply #15 on: 24/08/2006 12:54:41 »
quote:
Originally posted by syhprum

The movement of a condutive fluid (probably Iron) relative to the rtation of the earth in a layer immediatly above the earths solid core.


Just to Add: this movement happens in the presence of a magnetic field, and this produces an electric current, that, in turns, produces a magnetic field that reinforces the first, regenerating it (Dynamo theory).
How this can happen is however still a mistery for me, because, usually, an induced magnetic field is opposite to the first one (inducer).

The first (igniting) magnetic field could have been, for example, the one of another planetary object near the earth millions of years ago.
 

Offline syhprum

  • Neilep Level Member
  • ******
  • Posts: 3813
  • Thanked: 19 times
    • View Profile
Re: Physics Question of the Week
« Reply #16 on: 24/08/2006 19:03:05 »
It is well established that the earth early in its history was in collision with a mars sized object (Mars?) that lead to the creation of our moon, could this be the seed of the magnetic field?

syhprum
 

Offline ukmicky

  • Moderator
  • Neilep Level Member
  • *****
  • Posts: 3011
    • View Profile
    • http://www.space-talk.com/
Re: Physics Question of the Week
« Reply #17 on: 24/08/2006 20:03:38 »
quote:
Originally posted by syhprum

It is well established that the earth early in its history was in collision with a mars sized object (Mars?) that lead to the creation of our moon, could this be the seed of the magnetic field?

syhprum


Dont know but the way i see it is its got to have been a contributing factor as to why the magnetic field is  still so strong today as the colision  must have added heat to the outer core helping it stay liquid for so long.

Michael
« Last Edit: 24/08/2006 20:07:01 by ukmicky »
 

Offline syhprum

  • Neilep Level Member
  • ******
  • Posts: 3813
  • Thanked: 19 times
    • View Profile
Re: Physics Question of the Week
« Reply #18 on: 24/08/2006 12:11:20 »
The movement of a condutive fluid (probably Iron) relative to the rtation of the earth in a layer immediatly above the earths solid core.

syhprum
 

Offline lightarrow

  • Neilep Level Member
  • ******
  • Posts: 4586
  • Thanked: 7 times
    • View Profile
Re: Physics Question of the Week
« Reply #19 on: 24/08/2006 12:54:41 »
quote:
Originally posted by syhprum

The movement of a condutive fluid (probably Iron) relative to the rtation of the earth in a layer immediatly above the earths solid core.


Just to Add: this movement happens in the presence of a magnetic field, and this produces an electric current, that, in turns, produces a magnetic field that reinforces the first, regenerating it (Dynamo theory).
How this can happen is however still a mistery for me, because, usually, an induced magnetic field is opposite to the first one (inducer).

The first (igniting) magnetic field could have been, for example, the one of another planetary object near the earth millions of years ago.
 

Offline syhprum

  • Neilep Level Member
  • ******
  • Posts: 3813
  • Thanked: 19 times
    • View Profile
Re: Physics Question of the Week
« Reply #20 on: 24/08/2006 19:03:05 »
It is well established that the earth early in its history was in collision with a mars sized object (Mars?) that lead to the creation of our moon, could this be the seed of the magnetic field?

syhprum
 

Offline ukmicky

  • Moderator
  • Neilep Level Member
  • *****
  • Posts: 3011
    • View Profile
    • http://www.space-talk.com/
Re: Physics Question of the Week
« Reply #21 on: 24/08/2006 20:03:38 »
quote:
Originally posted by syhprum

It is well established that the earth early in its history was in collision with a mars sized object (Mars?) that lead to the creation of our moon, could this be the seed of the magnetic field?

syhprum


Dont know but the way i see it is its got to have been a contributing factor as to why the magnetic field is  still so strong today as the colision  must have added heat to the outer core helping it stay liquid for so long.

Michael
« Last Edit: 24/08/2006 20:07:01 by ukmicky »
 

Offline bostjan

  • Sr. Member
  • ****
  • Posts: 107
    • View Profile
Re: Physics Question of the Week
« Reply #22 on: 29/08/2006 07:37:31 »
i don't think that the theory is that well-established, since there are several, equally viable, competing theorys on the formation of the moon.

earth is very large for a rocky planet, so it's no surprise, really, about the outer core staying liquid.  a collision would be unlikely to add a significant ammount of heat to the outer core and not other parts of the planet, as far as i can understand.  perhaps you could clarify this conjecture?
 

Offline ukmicky

  • Moderator
  • Neilep Level Member
  • *****
  • Posts: 3011
    • View Profile
    • http://www.space-talk.com/
Re: Physics Question of the Week
« Reply #23 on: 30/08/2006 01:52:10 »
quote:
Originally posted by bostjan

i don't think that the theory is that well-established, since there are several, equally viable, competing theorys on the formation of the moon.

earth is very large for a rocky planet, so it's no surprise, really, about the outer core staying liquid.  a collision would be unlikely to add a significant ammount of heat to the outer core and not other parts of the planet, as far as i can understand.  perhaps you could clarify this conjecture?


The collision theory is the main and most widely accepted theory for the creation of the moon for many reasons. To name a few, the  moon and earth are the same age. The earth is tilted due to a very large impact and the makeup of the moon which has very little iron as most of it would have been propelled into the earth during the impact. Their are other
Michael
« Last Edit: 30/08/2006 02:02:28 by ukmicky »
 

Offline ukmicky

  • Moderator
  • Neilep Level Member
  • *****
  • Posts: 3011
    • View Profile
    • http://www.space-talk.com/
Re: Physics Question of the Week
« Reply #24 on: 30/08/2006 02:03:32 »
quote:
Originally posted by ukmicky

quote:
Originally posted by bostjan

i don't think that the theory is that well-established, since there are several, equally viable, competing theorys on the formation of the moon.

earth is very large for a rocky planet, so it's no surprise, really, about the outer core staying liquid.  a collision would be unlikely to add a significant ammount of heat to the outer core and not other parts of the planet, as far as i can understand.  perhaps you could clarify this conjecture?


The collision theory is the main and most widely accepted theory for the creation of the moon for many reasons. To name a few, the  moon and earth are the same age. The earth is tilted due to a very large impact and the makeup of the moon which has very little iron as most of it would have been propelled into the earth during the impact.


Michael
 

The Naked Scientists Forum

Re: Physics Question of the Week
« Reply #24 on: 30/08/2006 02:03:32 »

 

SMF 2.0.10 | SMF © 2015, Simple Machines
SMFAds for Free Forums