Physics 3 – Practical

I arrived at the school, found the correct corridor and hung around behind the melee of students, trying not to look too awkward. After being told about how the questions were divided, we split off into different labs. We were told which desk to sit at (confused teacher couldn’t figure out what I was doing there until he asked) and checked over the exam paper and equipment. Then we started.

You know what’s weird? Although I walked into the exam room, my physical intuition didn’t. I was entirely reliant on equations and what I knew to be true. I was so nervous that I just couldn’t figure out what *should* be happening, so had to go with what worked. For example, one experiment involved balancing a metre rule over a prism and attempting to determine the mass of a marble placed on one end of the rule, using moments. Not too tricky, but I was so worked up that I couldn’t figure out whether I should increase or decrease the distance of the fulcrum from the marble. I just changed it until it worked. I knew that if I could only calm down a little I’d be ok, but I couldn’t manage it. Still, at least I didn’t completely panic 🙂

The first experiment involved passing a current through a (an?) LED and a resistor and measuring the resistance of the former. We then had to swap out the LED and resistor, and try all combinations. Thing was, the resistance of the LEDs seemed to change depending on which resistor I used, which confused the hell out of me. As far as I knew, LEDs were like normal resistors and didn’t change their resistance. However, I couldn’t argue with the results and I couldn’t see anything wrong with my setup, so I went with it. I’m now pretty certain that the resistance of an LED does indeed change, and I’m not sure whether I should have known that. Still, hopefully I didn’t mess anything up too badly.

The most entertaining moment came when I was asked to measure the diameter of a ping-pong ball, without using calipers. As Ben pointed out, quite why they should ask me to do something so pointless is a good question. I couldn’t think of a clever scientific way of doing it, so I ended up holding the ball between two set squares and holding them over a ruler. Similarly, at one point I was asked to effectively find the height of a right-angled triangle, given only the hypotenuse. Well if there’s a way other than just measuring the damn thing, I don’t know it. Naturally none of the supplied rulers were long enough, so various contortions of set square arrangements ensued.

A couple of students were friendly enough to chat to me afterwards, which was nice of them. One more practical left, then it’s only ‘normal’ exams left.