OCR B: Advancing Physics - G494 (Rise and Fall...) 24/1/2012

Reply 80

Mill

Original post by ashton.gibbs

The first question, did you guys draw the velocity and KE graph the same? It really stumped me that one! haha

Nope I put velocity as a y=cos(x) curve, and kinetic energy was y=|cos(x)|

Reply 81

ashton.gibbs

Don't ya think there seemed to be so much more explaining type questions than there is on past papers?

Reply 82

ashton.gibbs

Original post by Mill

Nope I put velocity as a y=cos(x) curve, and kinetic energy was y=|cos(x)|

I thought about doing that but decided against it, since you can have negative velocity. Seems my silly little brain forgot a negative squared is positive :wink:

Reply 83

pinkprincess123

How did people find it?

Reply 84

croag

12

Thought this one was okay. Though that rounding thing got me, I just ignored it and carried on. One that I skipped and left to the end was the pressure, volume temperature one early on. I got it to be 3.2 x 10-7 or something.

That last question about root n and root t, yeah.. Didn't really understand that one. The multiple choice circuit one was a little weird too.

(edited 12 years ago)

Reply 85

ashton.gibbs

Original post by pinkprincess123

How did people find it?

Undecided! Any you thought were particularly hard?

Reply 86

jackofwack

Original post by Contrad!ction.

So, they got the units wrong for molar mass, and rounded 4.09 to 5. Brilliant.

Also, random walk, yay =/

I also noticed the strange rounding, it threw me a bit and made me think perhaps I got my conversion to Kelvin wrong...

I noticed the units were wrong for the bromine question too. It gave 0.16kg instead of 0.16kgmol^-1 didn't it?

What did you get for the time dialation question when it asked you to circle the correct time? I circled 6...not so sure of myself :'(

(edited 12 years ago)

Reply 87

ashton.gibbs

Original post by jackofwack

I also noticed the strange rounding, it threw me a bit and made me think perhaps I got my conversion to Kelvin wrong...

I noticed the units were wrong for the bromine question too. It gave 0.16kg instead of 0.16kgmol^-1 didn't it?

What did you get for the time dialation question when I asked you to circle the correct time? I circled 6...not so sure of myself :'(

ah, i circled 17 :frown:

thinking back i wish i'd have put 6 though, dayum!

Reply 88

StandbyExplosion

Apart from the energy questions with regards to gravity, I think that it went okay (I forgot to use r^3 from the previous part of the question)... I'm glad others are finding that using e as roughly kT gave them 4.09 and stating this was roughly 5, from past papers it seems that they can choose a number that is quite a long way off from their "about" value.

The final question confused most people I think... anyone able to explain that would be great. I answered it relating it to s=d/t equation but I did not know what else to do.

Good luck for March results :smile:

Reply 89

StandbyExplosion

Original post by jackofwack

I also noticed the strange rounding, it threw me a bit and made me think perhaps I got my conversion to Kelvin wrong...

I noticed the units were wrong for the bromine question too. It gave 0.16kg instead of 0.16kgmol^-1 didn't it?

What did you get for the time dialation question when it asked you to circle the correct time? I circled 6...not so sure of myself :'(

I got 6, 10/1.7 was roughly 6 :smile:

Reply 90

rogersnm

4

I think the logic behind the 5 was that if you do (3/2)kT then you get ~6 and if you do kT you get ~4. Either method is valid according to past mark schemes.

Reply 91

username456717

19

What did you guys get for the total energy, did you get it to be negative?
Also what about the mean speed of the particles?

Reply 92

rogersnm

4

Original post by StandbyExplosion

Apart from the energy questions with regards to gravity, I think that it went okay (I forgot to use r^3 from the previous part of the question)... I'm glad others are finding that using e as roughly kT gave them 4.09 and stating this was roughly 5, from past papers it seems that they can choose a number that is quite a long way off from their "about" value.

The final question confused most people I think... anyone able to explain that would be great. I answered it relating it to s=d/t equation but I did not know what else to do.

Good luck for March results :smile:

The number of steps a particle takes (N) is obviously going to be proportional to t, whether that's via s=vt -> N=vt or just N=kt. Once you do that you can just sub in sqrt(kt) and get an equation in the right format.

Original post by nebelbon

What did you guys get for the total energy, did you get it to be negative?
Also what about the mean speed of the particles?

I got a negative answer, I can't remember what it was though
iirc 270 m/s for the mean speed.

Reply 93

Ivo

3

I'm getting worried. For the last question about calculating energy released, did we need to convert from degrees to kelvin as I just took temp change to be 80 degrees centigrade.

Reply 94

ashton.gibbs

Original post by StandbyExplosion

Apart from the energy questions with regards to gravity, I think that it went okay (I forgot to use r^3 from the previous part of the question)... I'm glad others are finding that using e as roughly kT gave them 4.09 and stating this was roughly 5, from past papers it seems that they can choose a number that is quite a long way off from their "about" value.

The final question confused most people I think... anyone able to explain that would be great. I answered it relating it to s=d/t equation but I did not know what else to do.

Good luck for March results :smile:

My answer to the final question was pretty long winded. I put something like this...

x α √N and so x = k√N where k is a constant

More time allows for more steps, so N α t, and so N = qt where q is a constant

Since N = qt, x = k√qt = k√q√t, where both k and √q are constants
There fore x = C√t

... or something of the sort!

Is that the question you meant? haha :smile:

Reply 95

mishmash67

5

Original post by pinkprincess123

How did people find it?

it could of been worse i think, i couldnt get the conduction to increase :s-smilie:

Reply 96

rogersnm

4

Original post by Ivo

I'm getting worried. For the last question about calculating energy released, did we need to convert from degrees to kelvin as I just took temp change to be 80 degrees centigrade.

It's just a change in temp therefore it doesn't matter whether it's in centigrade of kelvin.

100 ^\circ C - 20 ^\circ C = 80 ^\circ C

373 K - 293 K = 80K

(edited 12 years ago)

Reply 97

ashton.gibbs

Original post by Ivo

I'm getting worried. For the last question about calculating energy released, did we need to convert from degrees to kelvin as I just took temp change to be 80 degrees centigrade.