Stellar Evolution     Stars form from enormous clouds of hydrogen atoms, pulled together by the force of gravity.  As the cloud collapses, gravitational potential energy is converted to kinetic energy of the atoms (they are all “falling” toward their common center of mass).  If a cloud has enough mass, the pull of gravity will [....]

Introduction to the Universe (IB Option E1)   209 Seconds video showing cosmic scales:      Powers of Ten video zooming out from earth to edge of universe :       A photo showing why the Milky Way is called that:       A photo showing stars moving across the night sky due to the [....]

Nuclear Physics and Radioactivity     Radioactivity is spontaneous and random.  The probability that an atom will decay remains constant for the entire life of the atom.  If you think about it, this is really strange.  How can it not matter whether a uranium atom is 1 million years old or 1 billion years old? [....]

Atomic Physics   Rutherford Experiment (aka Geiger-Marsden)       My summary   Rutherford shot alpha particles at a thin film of gold foil Most of the alpha particles went right through Some had high angles of deflection He was shocked when a small number of the alpha particles came zooming back out in the [....]

Thermal Energy Transfer / Greenhouse Effect    Some Background   IB calls this topic Thermal Energy Transfer, but really it’s about the greenhouse effect and climate change.  Calling it Thermal Energy Transfer it sounds more physics-y.     Climate change is of course a controversial subject.  Before I started teaching physics, I wasn’t quite sure [....]

The sequence of development of quantum mechanics, summed up for IB students, from me:   (1) Hydrogen atoms emit a discrete spectrum of light.  This is our first evidence that energy levels in the atom are quantized.  What a mystery!  Physicists have never seen something like this before.   (2) Balmer comes up with a crazy formula that predicts the [....]

a a Thermal physics provided the transition from macroscopic physics to microscopic physics, and electricity is all about electrons, so why are we backtracking now to talk about bouncing springs and wiggling strings?   It’s because waves are going to be essential, ultimately, to our understanding of the inner workings of the atom. Bohr’s earliest [....]

a I love physics, but I used to think this one topic, thermal physics, was boring.  I had to teach it twice before I understood it well enough to see how interesting it really is! a What makes thermal physics interesting is that it provides a link between the macroscopic world of Newton’s laws and [....]

a There are only four fundamental forces in physics, and in high school physics we will learn about three of them.  These forces are called “fundamental” because we don’t have a deeper explanation for why they exist.  The four are Gravitational Force Electric Force Strong nuclear force Weak nuclear force (we won’t learn about this [....]

a A force is just a push or a pull There are lots of ways to push or pull: Gravity pulls objects down toward the ground.  We call that force the weight of the object.   A string or rope can pull on an object.   Springs can do that, too.  That’s tension.   One [....]

a Free-fall:  a special case of uniformly accelerated motion a When you drop a hammer, it falls to the ground.  While it is falling, the only force acting on it is gravity. (There’s also a little bit of air resistance, but for a hammer moving at relatively low speeds, we can ignore that).  We call [....]

Yes we know. Fascinating and intriguing may not be the first descriptors that come to mind at the very mention of this topic. In fact, and also very unfortunately, it has been a sufferer of chronic neglect by generations and generations of students (and even teachers) 🙁 Mundane as it may seem, we cannot discredit this topic [....]

Defining Velocity Velocity is the rate of change of position. If you go in a straight line from A to B, your velocity is just the distance between A and B divided by the time it took to go from A to B. e.g. If the straight-line distance is 100 m, and it takes 20 [....]

Good job students, you’re halfway into the year and still surviving. Give yourselves a pat on the back, and take the mid-year break you all deserve after slogging away for six months straight. Go for a swim, an overseas trip, or just enjoy some time at home to rejuvenate your soul… On second thought, maybe [....]

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