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# The Physics PHYA2 thread! 5th June 2013 Watch

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1. (Original post by Jimmy20002012)
Bo problem

I have attached the question where you have to find the angle of incidence.

And also could you help the on 2c on the attached question, why doesn't the energy convert to kinetic energy?

Attachment 221724Attachment 221725Attachment 221726

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It is converted to KE also some is dissipated as heat due to friction between the baring surfaces

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2. (Original post by Jimmy20002012)
Bo problem

I have attached the question where you have to find the angle of incidence.

And also could you help the on 2c on the attached question, why doesn't the energy convert to kinetic energy?

Attachment 221724Attachment 221725Attachment 221726

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Hi! The GPE does converts to KE. However, not all of it converts to ke, some of it is wasted as sound and heat.
3. (Original post by StalkeR47)
Yep! I will help you! I am already helping a lot of people. But, which part do you need help with?
4. (Original post by Goods)
It is converted to KE also some is dissipated as heat due to friction between the baring surfaces

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According to the mark scheme all GPE is converted to thermal energy

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5. Can someone help me on this over tone rubbish please its so confusing and if you can go through question 4 ai and ii jan 2010 thanks guys
6. Also jan 2010 question 4bi
7. (Original post by susanjan123)
Sure! I did drew a diagram for you. Since it is only 3 marks, you can just give 3 details. Here is the attachment. I just did this for you. Sorry for the poor quality.
Attached Images

8. (Original post by VV.KKGSR)
Even though it's asking for kinetic energy, you have to use the potential energy formula mgh, so you just do 55*9.81*3.2

Also do you know how to do question 6di from this paper? It's only 1 mark but still can't understand it?

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I did that first but the mark scheme shows a different way, which I don't understand, and gets a slightly different answer.

And nope that was going to be my next question
9. June 2012 7bii - why does point P move upwards?
10. (Original post by Jimmy20002012)
According to the mark scheme all GPE is converted to thermal energy

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I think you have to mention that there is a little almost no overall change in ke. Most of it is transferred to heat and sound energy due to the friction and drag resistive force.
11. (Original post by Jimmy20002012)
According to the mark scheme all GPE is converted to thermal energy

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I guess where is says lost it means energy lost from the system therefore the energy lost as heat due to friction

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12. (Original post by stalker47)
sure! I did drew a diagram for you. Since it is only 3 marks, you can just give 3 details. Here is the attachment. I just did this for you. Sorry for the poor quality.
thank you!:d
13. (Original post by susanjan123)
thank you!:d
Your welcome! If you need any more help, ask me or others equally.
14. (Original post by StalkeR47)
I think you have to mention that there is a little almost no overall change in ke. Most of it is transferred to heat and sound energy due to the friction and drag resistive force.
How are you actually meant to know that, I at first put GPE-KE and some converted to heat due to work done against resistive forces. Why don't you gain any kinetic energy, i though you always gain it when going downhill?

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15. How would you solve question like question 5b June 2009?

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16. (Original post by Jimmy20002012)
How are you actually meant to know that, I at first put GPE-KE and some converted to heat due to work done against resistive forces. Why don't you gain any kinetic energy, i though you always gain it when going downhill?

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Yes you do gain ke when going downhill. However, the most gpe in converted to ke at the start, later on, most of it is wasted as heat and sound etc. I am not sure why the mark scheme says no gpe is converted to ke but only heat and resistive drag force.
17. (Original post by susanjan123)
How would you solve question like question 5b June 2009?

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Next half period would be time taken for the string to oscillate into one complete cycle divided by 2. This means you will have to explain the movement of point y with in the first half period. You will also have to write down where about the point y be after half period. Does this make sense?
18. (Original post by Micheal123456)
Can someone help me on this over tone rubbish please its so confusing and if you can go through question 4 ai and ii jan 2010 thanks guys
The first part is simple, you just draw a cuved dotted line above and below the line given to you. Basically two nodes and one antinode. The second part requires you to understand the first part - because you have drawn two of the dotted lines, the wavelength is double the original so you multiply 0.64 by 2 to get 1.28m as your answer.

For part bi you again draw your dotted lines above and below, but this time you have a space of 0.16m between nodes and so you divide 0.64 by 0.16 which gives you four. That tells you that you need to draw 4 half wavelengths, or two full wavelengths.

This stuff is hard to explain so I've attached a picture of what I did when I attempted this question a few days ago.

The picture may just be upside down
19. (Original post by Anonymous1717)
June 2012 7bii - why does point P move upwards?
Because the wave is oscillating and the points on the wave go up and down? Vibration is perpendicular to travel for transverse
20. (Original post by StalkeR47)
Next half period would be time taken for the string to oscillate into one complete cycle divided by 2. This means you will have to explain the movement of point y with in the first half period. You will also have to write down where about the point y be after half period. Does this makes sense?
Yes however I don't understand how it is positive maximum at a quarter of a period? Thanks

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