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Physics OCR A2 Pratical

vb07

well yeah
it was an experiment where u could have said a 100 different bad things about it
inspite of this, the values of K got pretty close to one another

my k values were about 15-20% away from each other so I just fudged the results a bit so they were within 10% of each other and say that they were proportional.

apart from that it was a pretty standard physics practical i thought.

Reply 21

sandettielightvessel

1

vb07

hehe pretty nice,
I got 1.10 mm for the slides, graph gradient = -0.0440 and intercept = 5.10, A was actually my V0 ie. 160 mV and B was 0.0440
The 50% thing was (ln 2/B) * (measurement of slide) - worked out around 17 for me. For the second question I said that T is proportional to root m, my two values of K were within 3% of one another.

Oooh yay - those tally roughly with what I got!

I did manage to almost knacker the micrometer though - got a disapproving look from the teacher. The invigilator was sat next to me the whole time doing what looked like a gripping crossword.

Reply 22

londonkid89

I was surprised with how little content was in part 2 (or is it that illusion of condensing most of the questions on one page rather than spreading it over a few pages)....

About the first part, I wasn't quite sure with the 50% Intensity thing (Might have got it wrong - oh well)

Reply 23

Charzhino

19

For my gradient I got -0.06mV. Inital reading was 218mV. Y-intecept i got 5.49. Micrometer thickness of the slides i got 1.49mm. The 'naturel log' bits where fine in my opinion. For the evaluation I put:

-Use displacement sensor or video footage to determine time period more accurately.

-Use fudicial marker.

-Use mechanical release mechanism to make sure oscillations are vertical which reduces sideway swings.

- Take more readings over wider range of masses.

Overall I thought it was a simple practical. The only questions I thought where tricky was the significant figures one and the one where it said, would using 1 thick slide intead of x still account for 50% of the light..

Reply 24

Charzhino

19

For my gradient I got -0.06mV. Inital reading was 218mV. Y-intecept i got 5.49. Micrometer thickness of the slides i got 1.49mm. The 'naturel log' bits where fine in my opinion. For the evaluation I put:

-Use displacement sensor or video footage to determine time period more accurately.

-Use fudicial marker.

-Use mechanical release mechanism to make sure oscillations are vertical which reduces sideway swings.

- Take more readings over wider range of masses.

Overall I thought it was a simple practical. The only questions I thought where tricky was the significant figures one and the one where it said, would using 1 thick slide intead of x still account for the same reading..

Reply 25

Baker

There are major flaws in these exams. Everyone gets every question right - you make a silly mistake and you end up with a C (especially considering how little marks there are on these papers, and the grade boundaries for every module in every subject)

Reply 26

Baker

I remember a maths exam (either C2 or M1) where I was sure I got 100% of the paper right, but only got 79/100 UMS. I asked for the paper back and low and behold I've got 71/75. 72 is an A. Absolutely ridiculous.

Reply 27

nervosa

i didnt really understand the 50% light intensity..can someone help me...how to work this out, it was really bugging me, because my thickness ended being something like 5mm and i know thats not right. im gutted because i think i forgot the minus on the gradient, dammit easy marks down the bin!!!

Reply 28

nervosa

oh was there supposed to be a relationship between t and (m)^1/2, looking by general consensus it looks like there is, but i didnt get one, oh no another one ive got wrong, dear oh dear..rubbish.

Reply 29

fblade

14

nervosa

oh was there supposed to be a relationship between t and (m)^1/2, looking by general consensus it looks like there is, but i didnt get one, oh no another one ive got wrong, dear oh dear..rubbish.

Yeah same here, I think I would have done better if I didn't have a cold :frown:

.

How did you guys find A and B that equation?

Reply 30

-G-a-v-

16

No big surprises with this paper I think - nice straightforward bog-standard practicals. Was very happy with it - left the last little 1-marker in the long experiment til the last minute though...and just as I was about to write down what I was fairly sure was the right answer we were told to stop writing - still, tis only 1 mark - was a nice exam really - but then again, physics practical exams are easy enough if you get enough practice at them. Just got the slightly less nice theory papers in June now!

Reply 31

corbinator44

you dont have to get a relationship to get the marks.

I did the reading I got for v at the start. divide that by 2. then by A. Ln that, divided that by - b and it got n. then n times the thickness of 1 will give the thickness which for me was 69 ish mm

Reply 32

corbinator44

the gradient didnt have a unit as it was a ln against n graph so no units, thats what i think anyway

Reply 33

-G-a-v-

16

Blah, I didn't mention the sideways oscillations :/ - but then it's 6 marks for the experiment and 2 for the written communication usually I think, and I made 3 criticisms and 3 possible improvements, I'll just have to hope all 3 of my comments were right :p:

Reply 34

corbinator44

wasnt it 8 and 2 artic?

Reply 35

-G-a-v-

16

corbinator44

wasnt it 8 and 2 artic?

Hope not

can't remember lol....ah well, its done now :p:

Reply 36

-G-a-v-

16

Gah - just looked at an old paper...it is indeed 8 and 2 ... and the sideways oscillation thing was an obvious one! Nevermind

Reply 37

7589200

18

A good check of your accuracy was to do e^intercept ie. your value for A and comparing it to your value for V0. Ideally, they should be the same.
Also, your values for the gradient, intercept, A and B, should be to 2.s.f/3 s.f. or at least a consistent standard.

Reply 38

Econometrician

If you were to experimentally calculate the power of a component (i.e a light bulb) what method would use?

Method 1

Put light bulb, battery pack, ammeter and rheostat in series, with voltmeter in parallel with light bulb. Vary and record I (by increasing resistance on rheostat) and record p.d on voltmeter. Then plot a graph of V against I, and the area under the graph is the power?(not sure about this one)

or

Method 2

Put light bulb, battery pack, ammeter and rheostat in series, with voltmeter in parallel with light bulb. Vary and record I (by increasing resistance on rheostat) and record p.d on voltmeter. Then plot a graph of V against 1/I, and the gradient is the power?

I really need help, i got a physics practical tomorrow

Reply 39

libertine17

Baker

There are major flaws in these exams. Everyone gets every question right - you make a silly mistake and you end up with a C (especially considering how little marks there are on these papers, and the grade boundaries for every module in every subject)

I'm really worried now, I was resitting it this june because I got a C in wave properties/ practical module last year,
and i forgot to put the frigging gradient as negative
****!

Physics OCR A2 Pratical

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