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Physics: Post your doubts here!

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On a different note, please solve my probs :). I have circled the parts I am facing problems in.
Q8bi)
Number = moles * NA (Avogadro's constant) = (1.2/235) * 6.022 * 10^23 = 3.08 x 10^21
(ii) Let lambda = L
Activity = LN
N = No*e^(-Lt)
N(krypton) = 3.1*10^21*e^(-0.231*3600) = 0 so activity = 0
N(barium) = 3.1*10^21*e^(-6.4*10^(-4)*3600) = 3.1 * 10^20 <------ This many numbers left after one hour.
So Activity = 6.4*10^-4 * 3.1*10^20 = 2 x 10^17
Total Activity = 0 + 2 x 10^17 = 2 x 10^17
 
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Q8bi)
Number = moles * NA (Avogadro's constant) = (1.2/235) * 6.022 * 10^23 = 3.08 x 10^21
(ii) Let lambda = L
Activity = LN
N = No*e^(-Lt)
N(krypton) = 3.1*10^21*e^(-0.231*3600) = 0 so activity = 0
N(barium) = 3.1*10^21*e^(-6.4*10^(-4)*3600) = 3.1 * 10^20 <------ This many numbers left after one hour.
So Activity = 6.4*10^-4 * 3.1*10^20 = 2 x 10^17
Total Activity = 0 + 2 x 10^17 = 2 x 10^17

In first part why did we take Atomic Mass of Uranium instead of Barium? That confused me. In second part why is N0 (initial) of Barium and Krypton taken as same?
 
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Can anyone state what is newtons law of gravity?
I write like this : It states that it is the force of attraction between two masses which is directly proportional to the product of that masses and inversly proportional to the square of the sepration of that masses.
If I write this, wont I get 3 marks?
 
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Can anyone state what is newtons law of gravity?
I write like this : It states that it is the force of attraction between two masses which is directly proportional to the product of that masses and inversly proportional to the square of the sepration of that masses.
If I write this, wont I get 3 marks?
You do get 3 marks but refer to point masses rather than just stating masses. Because one mark is for stating point masses in all the marking schemes
 
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Can anyone state what is newtons law of gravity?
I write like this : It states that it is the force of attraction between two masses which is directly proportional to the product of that masses and inversly proportional to the square of the sepration of that masses.
If I write this, wont I get 3 marks?
Newton's law of gravitation states that the force of attraction between two point masses is directly proportional to the product of their individual masses and inversely proportional to the square of their separation (or square of the distance between their centres).
 
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Can someone please explain these parts??
1. State the evidence that the spheres are conductors
2.state and explain the distance x at which the rate of change of potential with distance is a;maximum b;minimum
image.jpg
 
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Can someone please explain these parts??
1. State the evidence that the spheres are conductors
2.state and explain the distance x at which the rate of change of potential with distance is a;maximum b;minimum
View attachment 60498
1. Electric field strength inside the sphere is zero. From graph we can see E to be zero at some point, thus we can say spheres are conductors.
2. maximum potential at 11.4 and minimum at any points on graph where E is becoming zero, let us take it as 8 for an instance. As electric field sthrenth is zero at that point. We know a fair idea about E is proportional to V as electric field strength is the -ve potential gradient.
 
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(y) I mean what u dont get in the explanation part??
Work done = F*change in x.
Work done = Ep
Ep = F * 4 * 10^-2
This was the first way.
We know Ep = GMm/r
Now we know radius increases every year by 4cm.
So we know radius is changing so we can use the formula Ep = GMm(1/r1 - 1/r2)
r1 = orignal radius
r2 = 4 * 10^-2 + r1
This was the second way explained.

Now I asked u, what u dont get in this explanation, I will clear that.. ;)
 
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