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Answer my questions please!

  • Thread starter rocephin
  • Start date
  • #1
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Homework Statement


Question number 1:

I have read in my text book that absolute potential energy is

U= - Gmm/R

Now , my question is that if two bodies/particles are at a distance of 0.00008m or very close to each other so that the distance between them is nearly equal to zero , we will nee infinite amount if energy to separate them .

thus , U=∞
so how could particles at big bang separated then?

Question number 2:

In our text book , I have read that 80% of the mass of our universe comprises of Plasma , While surfing internet , I have read that 80% comprise of black matter.

My question is how black matter and plasma are interrelated?

Waiting for answers , thanks


Homework Equations



U= - Gmm/R
 

Answers and Replies

  • #2
445
5

Homework Statement


Question number 1:

I have read in my text book that absolute potential energy is

U= - Gmm/R

Now , my question is that if two bodies/particles are at a distance of 0.00008m or very close to each other so that the distance between them is nearly equal to zero , we will nee infinite amount if energy to separate them .

thus , U=∞
so how could particles at big bang separated then?
Gravitational force is not the only thing that affects bodies...
 
  • #3
gneill
Mentor
20,793
2,773

Homework Statement


Question number 1:

I have read in my text book that absolute potential energy is

U= - Gmm/R

Now , my question is that if two bodies/particles are at a distance of 0.00008m or very close to each other so that the distance between them is nearly equal to zero , we will nee infinite amount if energy to separate them .

thus , U=∞
so how could particles at big bang separated then?
It's not easy to get the centers of particles closer together than the sum of their radii. And for particles that are essentially point particles (such as electrons), there are other forces and principles that come into play at very close ranges (hence quantum physics).

Question number 2:

In our text book , I have read that 80% of the mass of our universe comprises of Plasma , While surfing internet , I have read that 80% comprise of black matter.

My question is how black matter and plasma are interrelated?
That would be "dark matter". Your book was most likely stating that 80% of the visible matter is in the form of plasma. It would appear that the matter we can see is not enough to account for the gravitational effects we can measure. Hence dark (invisible) matter. It looks like over 80% of what should be there can't be seen!
 
  • #4
1,679
3
The Newtonian gravity equation assumes point masses. If you have a uniform density of matter that fills all of space, the net forces on the matter would be zero.
 
  • #5
4
0
THanks
 

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