The Student Room Group
Competition - post a photo you've taken of nature >>
Competition - post a photo you've taken of nature >>
Competition - post a photo you've taken of nature >>

This discussion is now closed.

Check out other Related discussions

OCR PHYSICS B G492~ 9rd June 2014~ AS Physics

Scroll to see replies

Original post by CrystalPlanet
Haha thanks, I was just tossing in whatever I thought might get me the marks.

Any ideas on the water turbine question where it asked us why the energy supplied was lower?

I put water harder to push than air so more energy is used and heat energy I s lost in the generator coil through resistance in the wires. You?
Reply 241
Avatar for emfp21
emfp21
What was the finger one? Was it width or area?? I put 10^-4 because I thought it was area:/

Posted from TSR Mobile
I said the water will not always flow that fast

Posted from TSR Mobile
Original post by Bean man
I put water harder to push than air so more energy is used and heat energy I s lost in the generator coil through resistance in the wires. You?


Original post by DomStaff
1. The water carries on moving. Therefore doesn't transfer all of it's KE.

2. Mass of the turbines is a lot less so their speed may not be large enough for the same KE.

3. Absolute guess but part of the water may be reflected off some turbine blades and this slows down the water ahah, I just thought I'd throw another in there.


Good points there, I was stuck on this question for a few minutes.

I wrote that the flow of the water was turbulent rather than laminar so the turbines weren't able to generate enough rotation, hence less energy.

The water might have dissipated its energy by collisions with the surroundings such as the seabed and the rocks; all of it was not directed towards the turbines.

I wasn't the most confident person on this question haha
Reply 244
Avatar for emfp21
emfp21
Original post by CrystalPlanet
Good points there, I was stuck on this question for a few minutes.

I wrote that the flow of the water was turbulent rather than laminar so the turbines weren't able to generate enough rotation, hence less energy.

The water might have dissipated its energy by collisions with the surroundings such as the seabed and the rocks; all of it was not directed towards the turbines.

I wasn't the most confident person on this question haha


I put energy may be lost through sound and collision,and wind may be low - reducing speed?

Posted from TSR Mobile
Reply 245
Avatar for emfp21
emfp21
And for the flute question, she had to extend the flute right? And what did people put for the first 2 parts of that question??

Posted from TSR Mobile
Original post by emfp21
And for the flute question, she had to extend the flute right? And what did people put for the first 2 parts of that question??

Posted from TSR Mobile


Yeah.

1) somet like 260 cus it was 1.32 m and 340 m s^-1, giving lambda equals 257.5757 or something along these lines.

2) ANANANA

3 times fundamental frequency, therefore 3 nodes, all equally spaced. Antinode at each end.
Original post by emfp21
What was the finger one? Was it width or area?? I put 10^-4 because I thought it was area:/

Posted from TSR Mobile


I got that too.

Original post by emfp21
And for the flute question, she had to extend the flute right? And what did people put for the first 2 parts of that question??

Posted from TSR Mobile


Yeah, I think so. First 2 parts I think it was 258Hz? or something. And then you draw 3 half wavelengths in the tube
Original post by DomStaff
Yeah.

1) somet like 260 cus it was 1.32 m and 340 m s^-1, giving lambda equals 257.5757 or something along these lines.

2) ANANANA

3 times fundamental frequency, therefore 3 nodes, all equally spaced. Antinode at each end.


I meant frequency not lambda
Reply 249
Avatar for emfp21
emfp21
Original post by DomStaff
Yeah.

1) somet like 260 cus it was 1.32 m and 340 m s^-1, giving lambda equals 257.5757 or something along these lines.

2) ANANANA

3 times fundamental frequency, therefore 3 nodes, all equally spaced. Antinode at each end.


Oh:frown: got that but forgot to label the nodes etc. Was the finger area or width??

Posted from TSR Mobile
Original post by Knowing
I got that too.



Yeah, I think so. First 2 parts I think it was 258Hz? or something. And then you draw 3 half wavelengths in the tube


You get 0 marks for drawing it, just the position of nodes and antinodes. Well that is how it was on a past paper. I drew it just to make it easier to write where each thing was positioned.
Original post by DomStaff
You get 0 marks for drawing it, just the position of nodes and antinodes. Well that is how it was on a past paper. I drew it just to make it easier to write where each thing was positioned.



Original post by emfp21
Oh:frown: got that but forgot to label the nodes etc. Was the finger area or width??

Posted from TSR Mobile


Cross-sectional area.

I sat there and worked it out for me and it came closer to 10^-4 than 10^-6 and I have relatively skinny fingers hahaha.
Original post by DomStaff
You get 0 marks for drawing it, just the position of nodes and antinodes. Well that is how it was on a past paper. I drew it just to make it easier to write where each thing was positioned.


Yeah, that's fine lol, my drawing wasn't very neat anyway. I labelled them like you said too :smile:
Original post by DomStaff
Yeah.

1) somet like 260 cus it was 1.32 m and 340 m s^-1, giving lambda equals 257.5757 or something along these lines.

2) ANANANA

3 times fundamental frequency, therefore 3 nodes, all equally spaced. Antinode at each end.


I did everything there exactly as you put it; but I have a doubt, when I drew the standing wave I didn't get it to fit to the length of the pipe; only like 3/4ths of the pipe, will I lose a mark? I just drew it too short and realized my mistake. At the bottom I put another wave just in case.

Edit: oh I read your later post, I didn't know that you didn't get any marks for drawing it haha never mind.
(edited 9 years ago)
Reply 254
Avatar for STATER
STATER
3
Would it be valid to say something along the lines of currents in the water having different velocities and counteracting each other, so the resultant force on the turbine is less?
Original post by Knowing
Yeah, that's fine lol, my drawing wasn't very neat anyway. I labelled them like you said too :smile:


On the precious past paper it was open at one end not the other but I think the marking points were:

A at one end N at other
ANA...alternating
Correct pattern equally spaced.

So ours will be practically the same just A at both ends.
Original post by emfp21
And for the flute question, she had to extend the flute right? And what did people put for the first 2 parts of that question??

Posted from TSR Mobile


I can't quite remember what the question said...I think it was bringing the note down after the flute heated up? If so I put extend...mainly because I play the flute and that's what you have to do to make the note lower - literally had to go home and test it out straight away - then I based my explanation round that. I can't even remember what the first two parts where (blocking the memory since physics isn't my strongest subject :') )
For turbine question i put inertia of turbine blades and heat energy dissipated upon impact
Original post by STATER
Would it be valid to say something along the lines of currents in the water having different velocities and counteracting each other, so the resultant force on the turbine is less?


I considered writing this, but I'm not sure. It dead say the exact velocity of the waves at the top, so they may accept it or may reject it; we don't know. But don't worry.
Original post by DomStaff
I considered writing this, but I'm not sure. It dead say the exact velocity of the waves at the top, so they may accept it or may reject it; we don't know. But don't worry.


Yeah the question specifically said "subject to the conditions stated above", which implies there's only one velocity - the one given, so I think they'll reject the "different velocities" answer.

Related discussions

Latest

Trending

Trending

Articles for you