We started off with the simplest type of projectile - those that are projected horizontally. They therefore have an initial vertical velocity of zero so are pretty much the same as our calculations on bouncing balls and the like.
Things get a little more complicated when you launch projectiles into the air at an angle because the initial vertical velocity is no longer zero. If this is the case then you must think about the horizontal velocity and the vertical velocity separately.
We draw vector diagrams to simulate what we see in the real world. I think some people still don't get this.
As I see it, there are two main rules when drawing vector diagrams:
1. Join your vectors 'tip to tail'
2. Use your common sense!
If the resulting velocity, displacement or force looks wrong then use your common sense. Th diagram is only showing you what will happen if you put these two velocities together or these two forces together.
When we have more than one uncertainty to deal with, we need to choose which one to take into account for our final answer. To do this, we use the value that has the greatest percentage uncertainty.
The percentage uncertainty is expressed as a percentage whereas the absolute uncertainty is written as a number.
There are three types of uncertainty we need to consider for Higher Physics:
Reading; occurs when taking a measurement visually
Random; the subtle differences between experiments that produce differing results are caused by random errors
and Systematic; when there is something wrong with the equipment or the way in which it is used.
We can limit the effect of random errors by carrying out repeated measurments. You need to know how to calculate the mean and the error in the mean (approximate random uncertainty).
Now uploaded for the whole course. All of you should be working through these over the holiday, picking out the topics you find most difficult in the first instance. Any problems, give me a shout.
Look at the last device which uses p-type and n-type materials to conduct - the MOSFET. It will only switch on if there is a sufficient voltage across the gate of the transistor.
By putting some n-type and p-type materials together you can make all sorts of wonderful devices. Diodes, LED's, solar cells and LDR's all rely upon the technology of semiconductors. We explained how each of these devices work in terms of electrons and holes. You need to be able to distinguish between reverse bias and forward bias as well as photovoltaic mode and photoconductive mode.
Started semiconductors today. Semiconductors are, as the name suggests, materials that 'sort of' conduct electricity. We can add impurities to an element - the process is called doping - which allows the electrons to move. This can be done by adding an element with an extra electron (n-type) or by adding an element with one less electron (p-type).
Did more work on the Bohr model today. Energy is taken in by the electron to jump up one level or more and energy is given out in the form of a photon as the electron moves back down to its original level. The energy required to move from one level to the next can be displayed in an energy diagram. The bigger the gap between the lines, the more energy it takes to move between the levels. These energies are always shown as negative with the ionisation level (where the electron leaves the atom) being at 0 Joules.
If light and other electromagnetic radiations are made of photons then each photon must have an energy associated with it. This energy is E = hf. Thinking back to the photoelectric effect, we know that some materials will eject electrons when you shine radiation on them. The minimum energy required for this to happen is called the work function of the material. If a photon has an energy equal to this work function then it will cause an electron to be ejected to the surface. If the photon has an energy greater than the work function then the remaining energy will converted into kinetic energy of the photoelectron produced.