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Physics: Post your doubts here!

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Can you please explain 29, 26, 14 and 12 of the same paper. You don't need to solve it just explain the method.
12. As the balls are making an elastic collision so the speed of approach will be equal to the speed of separation. So use this concept to find the final speed of ball X.

14. The upthrust depends on the pressure difference. Since they have the same dimensions, this means that pressure difference is also same. So all the cuboids will have the same upthrust.

26. Is the answer D btw? I'll tell the method, if my answer will be correct :p

29. Find the phase difference between the two waves arriving at point Z like this (34-24 = 10cm). As the amplitude of oscillation is zero at Z this shows that destructive interference is occuring. So use the formula for distructive interference: (1/2 +n)λ = phase differece. So λ = phase difference / (1/2 +n)

Keep substituting value for n (1, 2, 3 so on) until you get a number which matches with the answer options..
 
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12. As the balls are making an elastic collision so the speed of approach will be equal to the speed of separation. So use this concept to find the final speed of ball X.

14. The upthrust depends on the pressure difference. Since they have the same dimensions, this means that pressure difference is also same. So all the cuboids will have the same upthrust.

26. Is the answer D btw? I'll tell the method, if my answer will be correct :p

29. Find the phase difference between the two waves arriving at point Z like this (34-24 = 10cm). As the amplitude of oscillation is zero at Z this shows that destructive interference is occuring. So use the formula for distructive interference: (1/2 +n)λ = phase differece. So λ = phase difference / (1/2 +n)

Keep substituting value for n (1, 2, 3 so on) until you get a number which matches with the answer options..
For 12 why can't we use the momentum before collision and momentum after collision thing?
For 14 Why does an object with a greater density meaning more mass since the dimensions are the same not exert greater pressure?
Yeah it is D.
 
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For 12 why can't we use the momentum before collision and momentum after collision thing?
For 14 Why does an object with a greater density meaning more mass since the dimensions are the same not exert greater pressure?
Yeah it is D.
Because we don't know whether their masses are equal or not Or what exactly are their masses. We could have used that, if we had either known their masses or had known that they are equal in mass.

Upthrust depends on the volume of fluid that is displaced by the object. Similar volumes of fluid are displaced. So similar upthrusts. Also that pressure is exerted by the the water molecules (or water) not by the cuboid.

I'll show you the method for 26 with diagrams. Give me 5 minutes :p
 
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Because we don't know whether their masses are equal or not Or what exactly are their masses. We could have used that, if we had either known their masses or had known that they are equal in mass.

Upthrust depends on the volume of fluid that is displaced by the object. Similar volumes of fluid are displaced. So similar upthrusts. Also that pressure is exerted by the the water molecules (or water) not by the cuboid.

I'll show you the method for 26 with diagrams. Give me 5 minutes :p
It still does not make sense to me. Th water is displaced not only by the water molecules but also due to the object and a denser object will displace more or whatsoever. :p
And sure.
 
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I don't know a proper method for it, but there's a very good way, that I use for solving such questions. It really works :p

upload_2016-3-31_11-56-35.png
Whenever you encounter such a question, place the tip of your pencil lightly on the paper. Then without moving your pencil, move the sheet of paper beneath in the direction opposite to the wave motion. Side by side as those humps arrive, move the piece of paper, up or down opposite to the position of the hump. Try it :p You'll get to know of this method. :p
 
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It still does not make sense to me. Th water is displaced not only by the water molecules but also due to the object and a denser object will displace more or whatsoever. :p
And sure.
Sorry, I think my explanations were vague. Okay let me describe the thing again:

The upthrust is the weight of water displaced. The amount of water displaced has nothing to do with the density. The aomunt of water displaced depends on the volume of the cuboid. Volume is same for all the cuboids, so they will displace equal amounts of water. So they will have the same upthrust. :p Clear now?
 
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I don't know a proper method for it, but there's a very good way, that I use for solving such questions. It really works :p

View attachment 59926
Whenever you encounter such a question, place the tip of your pencil lightly on the paper. Then without moving your pencil, move the sheet of paper beneath in the direction opposite to the wave motion. Side by side as those humps arrive, move the piece of paper, up or down opposite to the position of the hump. Try it :p You'll get to know of this method. :p
I can't visualise it lol I got the question tho. :p
 
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Sorry, I think my explanations were vague. Okay let me describe the thing again:

The upthrust is the weight of water displaced. The amount of water displaced has nothing to do with the density. The aomunt of water displaced depends on the volume of the cuboid. Volume is same for all the cuboids, so they will displace equal amounts of water. So they will have the same upthrust. :p Clear now?
YEAH THANKS REALLY.
 
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Guys does anyone have edexcel AS physics as a pdf or active book or know where to find it ??!!
 
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Can someone do part c please. Need it urgent.
Using the formula you proved above, you can find E, the Kinetic Energy required to statisfy their condition.
Next, using the relation E = VQ, you can find V. This is because the kinetic energy is being provided by the electric potential energy. You already know the charge and mass of an electron from the data provided at the beginning of paper.
 
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Paper 4 (A Level Structured Questions): The assessment of core and applications topics will be integrated. There will no longer be a section A and a section B.

What do they mean by the first statement ?
 
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Paper 4 (A Level Structured Questions): The assessment of core and applications topics will be integrated. There will no longer be a section A and a section B.

What do they mean by the first statement ?
The applications will be merged with the questions. There will not be a separate section B for applications.
 
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