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Edexcel Physics (Salters horners) 22nd May

_Jeb_

I thought PSA1 was harder than PSA2!

How did it go for you?

jeb

Reply 1

Salinger

1

i'm not too sure i thought psa1 was also harder, for the last part of the last question i didn't know what it was asking for

what did you get for the resitivitiy one on psa2 , i got 0.53 ohms, because i originaly had 83 but when checking through you used the thickness as the length, and the length given x width to work out the area, rather than thickness x width.

first q on psa2 did you get a range of frequencys - i got 4.8 x 10^14 hz to 8.something x 10^14 hz

other than that i thought most of it went ok

on psa1 i thought was ok, other than the dioptric lens, where it said draw what the ray should be, apparently the straight line to the left was the normal my physics teacher told me after lol :mad:

Reply 2

_Jeb_

OP

Hmm what was the last part? i can barely remember that! and for the resistivity how did you get 0.53 ohms??? cos i remember the question very well, it it said 0.4mm thickness, 0.5cm length and 0.3 cm width and it also said the resistivity was 2 ohm cm...and my question is did we have to convert it all to meters or leave it as centimeters

yea i did get the same frequencies! phew thank god!
oh god then i messed the dioptric lens one up!

And also the raindrop question in PSA2, what angle did you get for the angle of incidence?

jeb

Reply 3

Dragonkiller

1

What did you guys say the policeman's armour or something, was made from?

Reply 4

Salinger

1

_Jeb_

Hmm what was the last part? i can barely remember that! and for the resistivity how did you get 0.53 ohms??? cos i remember the question very well, it it said 0.4mm thickness, 0.5cm length and 0.3 cm width and it also said the resistivity was 2 ohm cm...and my question is did we have to convert it all to meters or leave it as centimeters

yea i did get the same frequencies! phew thank god!
oh god then i messed the dioptric lens one up!

And also the raindrop question in PSA2, what angle did you get for the angle of incidence?

jeb

resitivity q - thickness = 0.4 mm = 0.4 x 10^-3 m
- length = 0.5cm = 0.5 x 10^-2 m
- width = 0.3cm = 0.3 x 10^-2 m
- resitivitiy = 2 ohm cm = 2 x 10^-2 m

Using R = pl/A

remember it said shape was rectangle, so it was confusing because you used the THICKNESS AS THE LENGTH, and the LENGTH X WIDTH given for area

thus,

R = resitivity x thickness (length)
width x length (C.S ARea)

= (2 x 10^-2) x (0.4 x 10^-3)
(0.5 x 10^-2) x (0.3 x 10^-2)

= 0.000008 / 0.000015 = 0.533 ohms

i think its that, but i changed it to the above, after originally getting 83 ohms from doing the resitivitiy x length given / thickness x width.
but i believe it was above - resitivitiy x thickness (length)/ length x width (Area)

for policmen's armour - tough - can withstand dynamic loads on impact..

for projectiles on psa1 for the magnitude and direction - i got 33.4 degrees for direction

Reply 5

Dragonkiller

1

I also got 83 Ohms for that question. Not too sure if it's right now...

Reply 6

Salinger

1

Dragonkiller

I also got 83 Ohms for that question. Not too sure if it's right now...

i changed it from 83 to the above, after checking through
you think i'm right? im not sure

Reply 7

Dragonkiller

1

You're right if you were meant to use thickness as the 'length'. But I don't think they would have made it that confusing.

Reply 8

Salinger

1

Dragonkiller

You're right if you were meant to use thickness as the 'length'. But I don't think they would have made it that confusing.

yeah spose, but there were quite a few conversions to make on a lot of questions to trip people up i think, on the eye question for example as well, i think i ended up with 0.0003 m or something by using 1/f = 1/u + 1/v

what you get on psa1 football q for the part to work out direction and magnitude

Reply 9

Dragonkiller

1

Hmm, can't remember. I think I got 30 something for the direction, and magnitude I just used tan to resolve it.

Reply 10

michaelyus

10

Oh dear; looks like I have messed up PSA2 completely. A whole topic that I didn't quite revise in depth (though I think I made a competent effort); I though my resistivity question went OK until I saw that above; raindrop was generally acknowledged to be very tricky (I don't remember quite what I got - I remember writing something close to 50 degrees, and another for 20 degrees for parts of that question).

Reply 11

Salinger

1

i got 32.4 for direciton i think - you used tan for that

and for magnitude it was just pythagorus by squaring vertical and horizontal and then routing them... was 12.67 i think!

that was 4 marks so wasnt too bad

Reply 12

Dragonkiller

1

Lol ye, that's what I meant. PSA1 wasn't bad. I'm worried about PSA2 though :/

Reply 13

Dragonkiller

1

Raindrop question I absolutely messed up because I didn't draw the normal properly.

Reply 14

_Jeb_

OP

ohh crap! i screwed the resistance up! i calculated the volume instead of the area!!! bugger!!!

Reply 15

Salinger

1

i got 20.4 for the angle on raindrop by sin-1(1.3/the other angle)

and for critical angle 50.8 or something

jeb, i don't know if im right - i originall had 83 then changed it to that calculation above later on
whoever's right we should still get 2/3 marks for the question - right or wrong

Reply 16

Dragonkiller

1

Salinger

i got 20.4 for the angle on raindrop by sin-1(1.3/the other angle)

and for critical angle 50.8 or something

jeb, i don't know if im right - i originall had 83 then changed it to that calculation above later on
whoever's right we should still get 2/3 marks for the question - right or wrong

Ye, I got the same answers for the angles. But completely messed up the drawings.

Reply 17

Salinger

1

Dragonkiller

Ye, I got the same answers for the angles. But completely messed up the drawings.

i don't think i did my drawing's right, i was only used to drawing on straight block prisims, not circles - i was wondering where to draw normal etc. :eek:

Reply 18

_Jeb_

OP

Salinger

i got 20.4 for the angle on raindrop by sin-1(1.3/the other angle)

and for critical angle 50.8 or something

yea thats what i got :P phew! lol i am in college and trying to get hold of the paper we did yesterday! lolz! i am one of those people who likes to check it haha!

Reply 19

Salinger

1

_Jeb_

yea thats what i got :P phew! lol i am in college and trying to get hold of the paper we did yesterday! lolz! i am one of those people who likes to check it haha!

lol, you go to john leggot? ;P i go to franklin - you probably heard of it

i want a mark scheme i like to know where i've gone wrong/right

Edexcel Physics (Salters horners) 22nd May

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