[with respect to ex]

Hi Im a newbie. Does anyone have solutions for paper 2004 q 28b and 29 c and 2005 21 b please

[Lucy973]

(Original post by with respect to ex)
Hi Im a newbie. Does anyone have solutions for paper 2004 q 28b and 29 c and 2005 21 b please

2004
28b: 5.01x10^5 lines/m
29ci: 5.4x10^-7m
29cii: 2.3V

2005
21bi: Photoconductive
21bii:• Positive and negative charge carriers no longer
released (1)
OR electron/hole pairs no longer released (1)
OR (photo)diode no longer conducts (1)
OR resistance of (photo)diode increases/higher (1)
OR no current in (photo)diode (1)
• voltage across photodiode/YZ rises (above 2V) (½)
OR voltage input to MOSFET rises (½)
• causing the MOSFET to conduct (½)
OR switches on MOSFET (½)

[aroy45]

Someone help me know why the answer here is E

The q Is in the next post
This was posted from The Student Room's iPhone/iPad App

[aroy45]

Here's the q


This was posted from The Student Room's iPhone/iPad App

[TheUnbeliever]

(Original post by aroy45)
Here's the q

s = ut + 0.5at^2

[aroy45]

(Original post by TheUnbeliever)
s = ut + 0.5at^2

I did with with u= 3 t= 5 and a = -9.8 but it isn't working


This was posted from The Student Room's iPhone/iPad App

[benten17]

(Original post by aroy45)
Here's the q


This was posted from The Student Room's iPhone/iPad App

s=ut+0.5at²
s=-3x5+(0.5x-9.8x25)
s=-137.5
H=137.5m

It's descending so initial velocity is 3m/s but not in the +ve upwards direction, it's in the downwards direction so it's -3m/s

[TheUnbeliever]

(Original post by aroy45)
I did with with u= 3 t= 5 and a = -9.8 but it isn't working

You need to be consistent in your choice of axes - you choose -ve as down for your acceleration, but use +ve for your u (which should be downwards). Benten has the correct working above

[Lucy973]

(Original post by aroy45)
I did with with u= 3 t= 5 and a = -9.8 but it isn't working


This was posted from The Student Room's iPhone/iPad App

Both u and a need to be either positive or negative. They're about the same direction so u can't be positive while a is negative

[Lucy973]

Sorry didnt see this

[with respect to ex]

Sorry for paper 2005, i meant (a) (ii) not (b). I wasn't very clear; i know the answers but i want the working for it as well? Thank you.

[Lucy973]

(Original post by with respect to ex)
Sorry for paper 2005, i meant (a) (ii) not (b). I wasn't very clear; i know the answers but i want the working for it as well? Thank you.

2004
28b.
wavelength = 3^-9m
n = 1
angle = 18.5 degrees (37/2)

d= (n x wavelenth)/sin angle
= 6.33x10^-9/sin18.5
=2.0999x10^-8m

number of lines = 1/2.0999x10^-8 = 5.01x10^5 lines/meter

[Lucy973]

2004
29ci
E=3.68x10^-19 J
v=3x10^8 ms^-1

f = E/h
= 3.68x10^-19/6.63x10^-34
=5.55x10^14 Hz

wavelength = v/f
= 3x10^8/5.55x10^14
=5.4x10^-7 m

[rawragee]

I'm starting my revision tomorrow! I know I've left it a bit late, but I had my French exam today but now it's done so now I can actually focus properly it's looking like a weekend full of past papers and nothing else for me!

[..lauren]

(Original post by rawragee)
I'm starting my revision tomorrow! I know I've left it a bit late, but I had my French exam today but now it's done so now I can actually focus properly it's looking like a weekend full of past papers and nothing else for me!

I'm only going to fit in a couple of hours...
I have RMPS on Tuesday and I'm more confident with Physics, but I'm worried I wont get enough done :/

[kirstyhr]

(Original post by Sami')
When the gain is high enough, the amplifer saturates when the output voltage is about +/- 13V. A high gain therefore produces a sqaure wave output voltage.

Ahh, I see. that makes sense now. Thanks for your help!

[kirstyhr]

(Original post by ..lauren)
I'm only going to fit in a couple of hours...
I have RMPS on Tuesday and I'm more confident with Physics, but I'm worried I wont get enough done :/

Same here! I'm dreading Physics much more than RMPS... but all the same, I'm really not liking having to prepare for two exams one day after the other. How are you going about studying for them both?

[..lauren]

(Original post by kirstyhr)
Same here! I'm dreading Physics much more than RMPS... but all the same, I'm really not liking having to prepare for two exams one day after the other. How are you going about studying for them both?

Very, very badly! I've ended up studying for everything else... but I'm moderately fin for Physics, and I think I have time to cram effectively for RMPS.

You?

[Sami']

I have Physics Monday, Business Wednesday and Computing Thursday.

Business is easy but not looking forward to the other 2.

[kirstyhr]

(Original post by ..lauren)
Very, very badly! I've ended up studying for everything else... but I'm moderately fin for Physics, and I think I have time to cram effectively for RMPS.

You?

Pretty much the same as you! I can never study one subject for long before I feel that I'm neglecting my studies for the other subject and I switch. Not good! I think I'll end up cramming a lot of stuff for RMPS rather than Physics, just because I'm kind of terrified for the Physics exam, especially after the monstrosity that was Higher Maths...