Physics: Help

Guinea

By far my worst subject. Any suggestions as to what to study, as this weekend will be full of cramming. Oh god this isn't gonna be fun...

carlowboy

Start with your experiments. You have to really know all 25.

In section B, I'd recommend you read through all the questions 5,10(modern physics), 11 and 12. You're then left with one from mechanics, nuclear physics and electricity. There's one more but it could be unpredictable.

Nehpets

All the exps. They are worth 30% so this will help you pass easier.

Some exps to note: A proportional to F, Co-Planar forces, resistance of a metallic conductor or thermistor. You should learn them all though.

The learn your definition and derivations. This will be another 15% + depending on the paper.

Know particle physics, it's the easier of the two options and likely to come up. (It doesn't have to). With this get to know modern physics (radioactivity etc) very well.

Know about science and technology in society (STS) - basically know applications for things (wheatstone bridge, this is tipped to come up from one of those 606 shows)

4 marks = 1%, 3 marks for every peice of information. (So if it is a 12 mark question, mention atleast 4 things, 5 to be comfortable and 6 to be safe)

Now I just have to practise what I preach!! I'm in the same boat as you, cramming for the weekend!

carlowboy

motto for that paper seems to be: Easy come easy go.
They give you marks either but they take them off just as easy.

toxick

learn all the formulas, as they both can help with deffitions. look over all the experts, as they are nice easy marks. learn everyday application for certain objects, e.g prisms for parascopes ect.

Nehpets

Also for each exp (or most) know two points which might distrupt the results and know how to solve them. (This could be accuracy of newton balances, thermometers, friction, ways to reduce % error etc)

JC 2K3

carlowboy wrote:

motto for that paper seems to be: Easy come easy go.
They give you marks either but they take them off just as easy.

Yeah, just write SOMETHING if you can't think of the answer.

And give the experiments some time, once you know all the basic principles they're basically free marks. Remember the following:
-If there's a metre stick involved, you can ALWAYS use parallax error and zero error as sources of error.
-You can say avoid the above two errors to increase the accuracy of the experiment.
-If the graph they give you is straight through (0,0), the y axis is directly proportional to the x axis(and if the measurement on the x axis is 1/something it's obvioulsy inversely proportional to it, you know what I mean)
-If they ask you to draw a graph, be wary of the figures they give you, often you have to square them, get the reciprocals of them or get the sine of them or something, basically kow what your graph is trying to show.
-If know the formula that relates to the experiment, there's usually an easy 12-18 marks on offer for plugging in numbers they give you into it.
-If they ask you to calculate something from a graph, 90% of the time you just get the slope of the graph using the highest and lowest point.

eZe^

JC 2K3 wrote:

-If the graph they give you is straight through (0,0), the y axis is directly proportional to the x axis(and if the measurement on the x axis is 1/something it's obvioulsy inversely proportional to it, you know what I mean)
.

Word of advice, if your graph isnt on the exact (0,0) box you have to say a straight line graph NEAR the origin proves that x is directly proportional to y. If you say through the origin they are allowed to take 3 marks off you.

Guinea

Sweet. I'm gonna learn oh so much for Monday, and forget oh so much by Tuesday. Had I only paid attention in class...

JC 2K3

eZe^ wrote:

Word of advice, if your graph isnt on the exact (0,0) box you have to say a straight line graph NEAR the origin proves that x is directly proportional to y. If you say through the origin they are allowed to take 3 marks off you.

Tip for drawing graphs of direct proportion - scale them as small as possible and make sure they go through (0,0)

Nehpets

Does that not increase percentage error?

eZe^

Nehpets wrote:

Does that not increase percentage error?

Indeed, meaning that a calculation based on the graph has a higher chance of being outside the given range, resulting in 3 marks being lossed!

Nehpets

eZe^ wrote:

Word of advice, if your graph isnt on the exact (0,0) box you have to say a straight line graph NEAR the origin proves that x is directly proportional to y. If you say through the origin they are allowed to take 3 marks off you.

I didn't know that one, thanks! I just draw the line from the (0,0) to the points - the best possible straight line through the points.

i.e like this
but it might not go though ALL the points.
Is that allowed?

Fobia

Well, go for the middle ground - draw it a decent enough size, but of course draw your line so that it goes through 0,0 if at all possible (unless it's not supposed to!), eg even if it should be a little bit different with the figures, once it's not fiercely inaccurate you'll be ok with it, and with the calculations you can double check against figures you have to "wisely" pick your calculation points on your graph

eZe^

Fobia wrote:

Well, go for the middle ground - draw it a decent enough size, but of course draw your line so that it goes through 0,0 if at all possible (unless it's not supposed to!), eg even if it should be a little bit different with the figures, once it's not fiercely inaccurate you'll be ok with it, and with the calculations you can double check against figures you have to "wisely" pick your calculation points on your graph

I was just saying, if your graph has good distribution and a nice line but its only marginally off the origin, why risk losing a silly 3 marks when you can replace the word through with near...

carlowboy

but it might not go though ALL the points.
Is that allowed?

It is, as long as you have at least 5 out of 6 points plotted and the line is as close as possible to going through them.

Fobia

It doesn't have to go through a single one as far as I know - it's a "best fit graph". If you were being fiercely accurate, on a giant scale, the chances of it going through any would be extremely slim, so there's nothing wrong with this.

eZe^

As carlowboy said, you only need to have 5 of the 6 points plotted correctly, with the best possible fit you can get, try to make it that there is as many points above the line as below.

Nehpets

Yeah, that's the way I do them usually - just making sure

Foirfe

Just a quick few predictions:Doppler effect
a is proportional to f
Frequency is proportional to root of tension
specifc heat capacity's

carlowboy

Foirfe wrote:

Just a quick few predictions:Doppler effect
a is proportional to f
Frequency is proportional to root of tension
specifc heat capacity's

I'm thinking a light experiment (focal length of a concave lens) instead of frequency.

I'm thinking there could well be a full question on Induction.Scary

And nothing in Section B on light.

sully88

I think the doppler effect could be on the STS regarding the "red shift". I think that x-ray produaction or cathode ray tube (diagrams) explanations could be up. If they dont ask the wheatstone bridge this year they never will. The definition of sound intensity I think will be on the paper as well.

Turnip2000

sully88 wrote:

I think the doppler effect could be on the STS regarding the "red shift". I think that x-ray produaction or cathode ray tube (diagrams) explanations could be up. If they dont ask the wheatstone bridge this year they never will. The definition of sound intensity I think will be on the paper as well.

Red shift eh?? So is that on our course?? Cause thats the first ive heard of it?

JC 2K3

eZe^ wrote:

Indeed, meaning that a calculation based on the graph has a higher chance of being outside the given range, resulting in 3 marks being lossed!

But they give you the points and all you have to do is calculate the slope....

JC 2K3

Turnip2000 wrote:

Red shift eh?? So is that on our course?? Cause thats the first ive heard of it?

I think it's that starts look red when they're moving towards us due to the Doppler effect or something?

rjt

JC 2K3 wrote:

I think it's that starts look red when they're moving towards us due to the Doppler effect or something?

More or less. I *think*, that by the Doppler effect, because other stars are moving away from us (universe is expanding and whatnot), the wavelength of light appears to be longer than it really is. So light is shifted down to the red end of the spectrum. By comparing how 'red' the light appears with what colour it should really be, we can calculate the speed at which the star is moving away from us.

But it's been a while since I did this section, so may not be entirely correct.

Limerick Dude

rjt wrote:

More or less. I *think*, that by the Doppler effect, because other stars are moving away from us (universe is expanding and whatnot), the wavelength of light appears to be longer than it really is. So light is shifted down to the red end of the spectrum. By comparing how 'red' the light appears with what colour it should really be, we can calculate the speed at which the star is moving away from us.

But it's been a while since I did this section, so may not be entirely correct.

I just read over that today, i think you got it more or less correct

JC 2K3

Ah, should have said "moving away from us" then.

On a side note, I just did a couple of exam Qs in Physics and got most of it all right. I shouldn't have taken most of today off probably, but I'll do loads tomorrow.

I'm thinking Chemistry mornings and Physics evenings for the next few days, with an App Maths Q or two in between

eZe^

Has anyone else been taught to put the independant variable on the x axis and dependant variable on the y axis as standard procedure for graphs?

JC 2K3

Yes, but I don't see how it makes a difference.

Fobia

eZe^ wrote:

Has anyone else been taught to put the independant variable on the x axis and dependant variable on the y axis as standard procedure for graphs?

Yeah, but you're gonna have to learn off the axes for most of the LC ones anyway, so no use to you in the exam really!

eZe^

JC 2K3 wrote:

Yes, but I don't see how it makes a difference.

If you ever take lectures in physics beyond L.C its apparently a massive difference. The lecturers get really pissed off if you dont, its just scientific convention apparently. I find it helpful because Ive personally gotten used to using y = mx with the dependant on the y axis... It makes no difference really and can sometimes make calculating the slope more complicated (like I think in F against A the mass is actually the reciprocal of the slope) but why not get into conventional habits, making it easier for me in college.

Limerick Dude

I have alot to cover in physics.

Still have to go over most of my experiments.

The aspects which im going to go over are radioactivity + electron(all the junk), particle physics option,most of electricity (everything cept capacitance), heat and mechanics.

Leaving out light, and magnetism stuff.

I really hope a full question comes up on radioactivity or the electron. and maybe even a part of question 12 on top of that.

Nehpets

You have 3 days? Not much of an excuse to leave anything out

Tomlowe

JC as far as I know, you have to take points from the graph that you've drawn to get the slope, not from the data you're given, because your graph is supposed to be the one that averages the values you're given... so if you just take 2 of the points then that doesnt take into account the other values

Turnip2000

Limerick Dude wrote:

I really hope a full question comes up on radioactivity or the electron. and maybe even a part of question 12 on top of that.

Dont be setting your heart on fussion and fission cause it aint gona feature in a big way... it has for the last 2 years and theres only so much they can ask. Its been an sts question aswell so ders one out da window:(

Im leavind out light and sound but still doing the doplar because that has to get a full Q this year and there aint that much to it.

JC 2K3

Tomlowe wrote:

JC as far as I know, you have to take points from the graph that you've drawn to get the slope, not from the data you're given, because your graph is supposed to be the one that averages the values you're given... so if you just take 2 of the points then that doesnt take into account the other values

Honesly, this is being analysed far too much, if a feckin graph. It's possibly the easiest 12-18 marks you'll get in your physics exam, and they really are not hard at marking it at all. There's no bonus for neatness/absolute precision here. You just plot the points, draw a line that goes through most of em, pick 2 points on the line and get the slope. Most of the time only one or two points they give you are not on the line, so ignore them.

WildCardDoW

I suck at grpahs, I always make stupid mistakes! I get the question right, but i waste so much time on them, it's sad.

Limerick Dude

Nehpets wrote:

You have 3 days? Not much of an excuse to leave anything out

Yes plus the study I have to do for economics!

Limerick Dude

JC 2K3 wrote:

Honesly, this is being analysed far too much, if a feckin graph. It's possibly the easiest 12-18 marks you'll get in your physics exam, and they really are not hard at marking it at all. There's no bonus for neatness/absolute precision here. You just plot the points, draw a line that goes through most of em, pick 2 points on the line and get the slope. Most of the time only one or two points they give you are not on the line, so ignore them.

Exactly, nothing warms my heart more when they ask you to draw a graph in an experiment and they are giving you laods of marks for it!

cormac17

im dreadin physics!!!,,but just hopin 4 a C3, have accounting on monday 2,,nd economics on weds,,so this will not b an enjoyable weekend at all!!:(:( wish i was finished!!!,,ne one else av acc nd physics??

sternn

afriad not, i have spanish and physics which isn't too bad. All i really need in physics is a pass...and basically all this weekend im learning all the formule, definitions and experiments, and leaving it at that. Im afraid i cant do anymore, and the rest of the stuff is going to have to come from memory over the past few years. Hopefully that will get me a C.

Schlemm

Whatever you do, don't forget the UNITS!!
And write down which formula you're going to use!