Examination FEVER : for your eyes only

Now is the time again to press the panic button. The exam starts off with practicals. You are worried about the Physics practicals especially the girls. Mention of Physics usually sends the shivers up and down their spine. All I can say is "don't put undue pressure on yourself". You can always tell who are the JPA students in the examination hall : those stern faces compare to the worriless faces of those non JPAs. Just try to relax a little and you be surprise you actually could do better.

What we have gone through during our normal practical classes should be good enough to take you through the practicals without sweat:- unless your short memory play tricks on you again that you forgotten what I told you what to do and what not to do.

Your practicals will be set on topics from mechanics, electricity or heat. Usually only two of them will be set but in 3 experiments.

In mechanics:-

In oscillations or vibrations, time for 5, 10 or 20 oscillations and then find the period. How many ? Well do a trial run to see 10T>11 seconds or not. If not, next one will be 20T and not 12T or 15T. We usually take the minimum as 10T.

We did quite a lot of experiments on motion down the slopes (runway ). Well, be sure to draw a simple diagram to show how you measure the dist. traveled by the trolley, tennis ball or the glass sphere. If the time down the slope is less than 2.0 s, repeat 5 times to get the average. Your eye should be level at the point of release or the stop line. Don't forget to show how to measure the height to calculate the gravitational potential energy. If measurement of angle of slope is required, then usually one of the length will be fixed and you measure the other length to find tan, sine or cosine of the angles. Most of the time, you can't measure the angle directly. If it is extension of spring like what we did, have a column for scale reading (reading direct form the metre rule) before calculate the extension. See the graph, if the graph require the extension in mm, do the scale readings in mm as well.

In experiments involving moment, remember the technique to determine the centre of a slotted weight or stack of coins, hence the distance from the pivot.

In electricity:

Make sure the contacts are good. Make sure the crocodile clips close their mouths, otherwise they will bite off your mark in the sense that your readings may not be good. Normally the voltmeter will be in 2 decimals and the ammeter (usually measuring mA) may have no decimals or 1 decimal the most.It should be anounced to you in the exam. When the readings fluctuate, take the one which stays for quite sometimes. Don't wait for one hour to take the reading, it should be steady within 5 seconds.

In Heat

Don't forget to stir the liquid with the stirrer (not thermometer of your finger, your finger might contaminate the liquid) The temperature reading should be taken at 30 seconds intervals so that you have enough readings for a smooth curve. Heat experiment graphs are usually curves.

You should develop appropriate techinques to generate results wich are as accurate and reliable as allowed by the apparatus such as :--

zero error checks

repeat measurements ( at different places if appropriate)

Eye level to avoid parallax error

use of marker at centre of oscillation to aid timing

use of set square for checking vertical or horizontal arrangements

Remember how to find the % of difference. Remember the denominator (pembawah) should be the average values if both values are from your experimental results but it should be the standard value if one is given. Use you value to ascertain the relationships ( between the physical quantities of course ). 10% is the norm for experimental uncertainty.

Recently you are required to investigate further the relationship ( usually given in equations) of the experiment done. I think we have done two of such experiments. But just to remind you, remember

to study the equation carefully and identify which were the constant terms. write down and tell the examiner, (don't tell me later after the exam. I will knock your head for that)

which quantity you wish to vary, and then

which quantity to observe and measure/record (don't just observe and do nothing, you get nothing for nothing done)

Remember to repeat the procedure/experiment by using different values of "which quantities" and record the "corresponding values of which quantity. eg vary A and record the corresponding B values.

then plot what against what

state the expected shape of graph and lastly

what quantity can be found ( from y-intercept or from gradient) if the quantity cannot be found directly from the gradient, show how to get it. eg. k=1/gradient or k=(gradient) x2 etc.

The above were written just as they pass through my mind, I may miss out something. Feel free to drop me a line if you have doubts. Don't ask me what you should take for breakfast but it is ok if you ask me what I like to have for breakfast.

Good Luck to all of you.