Physics P1

I'm reading the Paper 1s now, but before I write anything, I've decided that the best tip for this paper is:

Get a good night's sleep

Seriously, this paper has to be finished in one hour, so what's important is your condition. You'll need to be able to read and comprehend questions quickly and answer them accurately. If you want to study, study now so you can go to bed early. (Lol Ken)

Since Paper 2 was an English paper and doesn't have a lot of difficult calculations or definitions, expect the opposite for Paper 1, though I wouldn't rule out the possibility of an English MCQ.

The time distribution should be: 40 minutes for answering questions, (Skip the ones that you can't) 10 minutes for answering questions that you've skipped, and another 10 minutes to check your answers. This is, of course, the ideal distribution, but if you think this is unrealistic, then change it according to your needs.

If you are unsure of an answer, or you have skipped a question, then mark that question/answer with a tick (or any other symbol) with a pencil on the answer sheet. This way, when re-checking your answer/completing the missed ones, you won't waste time going through the paper again. (Remember; 1 hour!)

Update: Jusk ask me tomorrow if asking specific details on Paper 1, or Albert, or Ken, or Vika, or Daniel.

Physics P1, P2

Since superscript letters doesn't seem to be supported here (Exception are presets), please take note that the [^] sign translates to 'to the power of'. (e.g. 10^-6 means ten to the power of minus six)

Random General Tips

• DON'T PANIC (Printed in large, friendly, and yellow letters)
  
• Be concise, precise, accurate, clear, complete, and coherent when you are asked to define. (This is also why definitions are the hardest things in physics. Believe me)
• Use multiple short sentences for definitions, one point per sentence. This way, your answer is direct and easily understood. (As your English sucks, you are more likely to obscure the meaning should you put long sentences)
• In diffraction grating, n is always rounded down to the lowest integer. (e.g. n =2.8, so when rounded, it becomes n = 2, not n = 3)
• Read, comprehend, and read again the question. Seriously.
  
• When encountering an unfamiliar sum, the first thing that you must do is to find out which laws to apply to the sum. This is extremely important. (For proof, read question number 2bii, paper 2, physics, summer 2008; was your first thought the principle of conservation of momentum?) Second, attack the sum in a logical manner; never ever ever ever assume anything, and always start from facts given by the sum. Third, a particular sum could involve materials from any chapters, so don't be so narrow-minded and confine your thinking in only one direction; be creative.
• Sometimes, they require you to write the equations in words first (i.e. Work done = area under graph line) before moving on to symbols. (i.e. W = ½Fx) This usually appears when you are asked to prove something.
• When drawing field lines, draw at least (To 6.
  
• May/June 2006's Paper 2 is one of the hardest in the repertoire, (But honestly, I think it is the hardest) so go check that.
  

Chapter 1 - Physical Quantities and Units

All quantities consist of a numerical magnitude and a unit.

The six basic units (In S.I. units) are:

• mass (kg)
• length (m)
• time (s)
• current (A)
• temperature (K)
• amount of substance (mol)

Derived units consists of basic units. (e.g. Velocity is displacement over time [m/s], charge is current times time [As])

Physical equations must be homogeneous. Examples:

• v = u + at (Homogeneous; v is [m/s], u is [m/s], at is [(m/s²)*s] = [m/s])
• v² = u² + 2at (Not homogeneous; v² is [(m/s)²] = [m²/s²], u² is [(m/s)²] = [m²/s²], 2at is [(m/s²)*s] = [m/s])

List of prefixes:

• pico [p] = 10^-12
• nano [n] = 10^-9
• micro [μ] = 10^-6
• mili [m] = 10^-3
• centi [c] = 10^-2
• deci [d] = 10^-1
• kilo [k] = 10^3
• mega [M] = 10^6
• giga [G] = 10^9
• tera [T] = 10^12

Should you ever need to estimate physical quantities, there are 2 things that you must do: 1) Use your common sense, and 2) Common sense.

Scalar quantities have only magnitude and unit, while vector quantities have magnitude, direction, and unit. (e.g. Energy [J], Distance [m] are scalars; force [N], momentum [Ns] are vectors)

In doing equations, the product or division of two vector quantities would result in a scalar quantity, while the product or division of a scalar and a vector quantity would result in a vector quantity. (e.g. Force (Vector) times displacement (Vector) equates to energy (Scalar), acceleration (Vector) times time (Scalar) equates to velocity (Vector))

Vectors can be added or subtracted only if they are coplanar. (i.e. On the same plane; vectors in the x-direction can be added or subtracted, but not vectors in x-direction with vectors in y-direction)

If wishing to add non-coplanar vectors, it is necessary to split the vectors into perpendicular components. (Most of the time, into x-and-y-directions)

Chapter 2 - Measurement Techniques

Formulae in this chapter:

• Δa/a = Δb/b + Δc/c + ... + Δz/z (Fractional uncertainty)
  

Systematic errors,

• causes a set of readings to be either too high or too low from the true value.
• cannot be eliminated or reduced by averaging.
• include: Unaccounted zero error in measuring instrument; using a damaged or poorly calibrated instrument; reaction time not accounted for. (e.g. When using stopwatches)

Random errors,

• causes a set of readings to have generally high scatter. However, the end result could still be accurate.
• can be reduced by averaging.
• include: Parallax error, changes in wind speed and/or direction, changes in temperature, fluctuations in pressure, etc.

Precision refers to the distribution or scatter of values about the true value. A set of readings is said to be precise if it has low scatter.

Accuracy refers to the trueness of values. A set of readings is set to be accurate if the readings are about the true value of the reading.

Therefore, a set of values with very few random errors can be said to be precise, while a set of values with negligible systematic error can be said to be accurate.

Example: (Doing an experiment to find the value of g)

• g = 8.93, 9.34, 9.01, 8.77 (Not precise and not accurate)
• g = 9.34, 9.35, 9.33, 9.34 (Precise, but not accurate)
• g = 9.66, 9.81, 9.99, 9.78 (Not precise, but accurate)
• g = 9.79, 9.82, 9.81, 9.81 (Precise and accurate)

Uncertainty arises because a quantity may never be measured exactly. (e.g. Even if it looks like you've measured 25 cm on a plastic ruler, the actual value could be 25.0012312753 cm)

The uncertainty of a measurement usually is taken from the smallest scale of the measuring instrument (e.g. Suppose you've measured 24.3 mm on the vernier caliper. The smallest reading the vernier caliper can take is 0.1 mm, therefore, the reading is written as: 24.3 ± 0.1 mm. This means that the exact value of the reading is between 24.2 to 24.4 mm)

The fractional uncertainty of a measurement is the ratio of the uncertainty of the measurement over the read value. (Using the above example, its fractional uncertainty is given by [Δx/x] = [0.1/24.3])

The percentage uncertainty of a measurement is its fractional uncertainty expressed in percentage form. (Again, using the above example, the percentage uncertainty is given by [(Δx/x)*100%] = [(0.1/24.3)*100%])

When arithmetically operating on readings with uncertainties, always apply the fractional uncertainty formula. [Δa/a = Δb/b + Δc/c + ... + Δz/z, where Δa represents the uncertainty of quantity a, Δb quantity b, and so on]

For example, you are asked to find the answer of [(5 ± 1)*(7 ± 2)]:

• Δa/a = Δb/b + Δc/c
• (Δa/35) = (1/5) + (2/7)
• Δa = 17
• Answer = 35 ± 17

The 5 and 7 are multiplied as usual, but this is not the case with the uncertainty. This is why it is recommended to stick to the formula.

When measuring distance using a ruler, you are actually measuring two points and taking the difference between those two points. Therefore, the uncertainty should be doubled. (e.g. Smallest scale on ruler is 1 mm. You measured 250 mm. The uncertainty would be 250 ± 2 mm)

Chapter 15 - Waves

The electromagnetic spectrum:

• Gamma-rays (10^-14 < λ m < 10^-11)
• X-rays (10^-11 < λ m < 10^-8)
• Ultraviolet (10^-11 < λ m < 4 * 10^-7)
• Visible light (3.8 * 10^-7 < λ m < 7.5 * 10^-7)
• Infra-red (7.5 * 10^-7 < λ m < 10^-3)
• Microwaves (10^-3 < λ m < 1)
• Radio waves (1 < λ m < 10^9)

Physics AS P3

Okay you people, Sir Puran has been kind to say most of there is to know about Paper 3, so this part of the exam shouldn't bee too much to worry about. I'll list some points to remember when doing this paper.

I ran out of time, so I wouldn't say that this would be a complete work, but I hope it'll still be helpful.

I've covered all aspects of graph-making (I hope), and some of measurements. However, I'm unable to post a say on the others, so I really encourage you to read this particular handout:

PHYSICS A/AS
9702

DEFINITIONS AND FORMULAE

That's the title of the handout, but that part is none of our concern; what's important in that paper is the next part; it has all the information minus graph drawing. (Nearly a bible, but hey, I did graphs already; scroll down)

If you're not reading it, then it's your own problem if you lose marks because some idiot asks you to plot the graph logarithm style, or if you mess up your significant figures.

Measurements

• Read and follow the instructions carefully to the letter.
• Wherever your common sense tells you to, take repeated readings. (Usually around 4 to 6 times) Also, make sure these repeated readings are not uselessly repeated. (e.g. Measuring the diameter of the wire at the same location and without rotating it. Go figure why)
• Be aware of the Power of Tens.
• And check your formulae.
• Do make sure that you have utilised most of the given range in taking your measurements. (i.e. If given a range between 0 to 1 metre, at least use 0.1 to 0.9 metres)
• The difference between each measurement should be roughly equal. (i.e. Take, for example, 0.2, 0.4, 0.6, 0.8, and so on)

Graphs

Since I lack the software needed to draw graphs + I'm too lazy to make one on mspaint.exe, there will be no illustrations here.

Also, since it has been ages since CIE released a paper where candidates are required to plot a curve, I suggest you bring your flexible ruler.

Anyway,

For graphs, here are the 5 points to remember:

• Choice of scale
• Plotting of points
• Line of best fit
• Calculation of gradient
• Determination/calculation of the y-intercept

Choice of scale

• You must make sure that the scale you choose will make your graph occupy more than half of the graph paper.
• Label the axes. (Include the quantity in question and its unit)
• Make sure that your scale is conventional! (As in: Don't make it so that people will have to read it right to left, like Arabian script; etc.) Remember this when plotting negative numbers, ja?
• No fancy scales. That means on the big squares, don't try using 3, 6, 9, 12, etc. or anything that 1) Makes it hard for you to read, and 2) Makes it hard for you to plot.
• It is recommended to not leave space for labeling each big square. (i.e. Do: 0, 5, 10, 15; not 0, nothing, nothing, 15)
• Scaling must also be regular. (e.g. 5, 10, 15; not 5, 11, 20)

Plotting of points

• Don't plot outside the given area/margin. (Outside the big, boxy thingies)
• All data must be plotted. (e.g. If you have made 7 observations, the examiner must see 7 plots in the graph)
• If you must plot let's say, 0.43 m, and your smallest box represents 0.2 m, you will have to approximate this plot. The room for error given by the examiner is half of this value. (In this case, ± 0.1)
• The plot must be clear enough for the examiner to see.
• Don't make your plots very thick, as they examiner may not be able to see accurately whether you have plotted the corresponding observation correctly in the graph, resulting in the loss of marks. It is also due to this that you use crosses to mark plots and not dots.

Line of best fit

• There must be at least 5 plots for the 'best fit' mark to be awarded. (No problem, really, given that the question usually requests for 6)
• The line of best fit must be 'balanced', at least roughly. Simply put, if you have 3 plots above the line of best fit, then have 3 plots below the line of best fit too.
• Lines must thin and clear. This is not an art examination, so avoid unnecessary ornaments like making thick lines and having jembut branch from it et cetera et cetera. Curves are usually prone to this. (Let's hope you didn't throw away your flexible ruler)
• Lines must extend reasonably further than the last greatest plot, reach x = 0, but not extend to less than x = 0. (At least so far, don't ask me if this still applies if we have to plot both negative and positive values)

Calculation of gradient

• Make a right triangle to indicate from where are you taking the coordinates to include in your calculation.
• Take the coordinates which lie on the line of best fit, not from the plot which is used to make the line of best fit.
• Indicate those coordinates in the graph. (e.g. If you take one value to be (1.24, 3.22), then write (1.24, 3.22) on (1.24, 3.22) on the graph)
• The triangle must cover more than ⅔ of the whole curve.
• ∆y and ∆x must be accurate to the smallest square in your graph.
• I cannot say if we would need units for the gradient, since my own experience and various sources conflict. Therefore, use your own judgment, or go ask somebody credible.
  
• Workings workings workings! Show them!

Determination/calculation of the y-intercept

• y-intercept is always read from x = 0, x = 0, x = 0.
• If you cannot read the y-intercept of the graph, then you have to calculate it using the equation y = mx + c. To do this, take any value from the line of best fit and substitute those values into the equation. (I'm not sure, but to be on the safe side, do indicate these values on the graph, like you would with a gradient-calculation coordinate)
• The y-intercept has units. (Usually)