The stunt is performed by a guy who claims to have invented a zero-friction material. If he’s right, all of the jumper’s gravitational potential energy at the top of the slope is turned into the kinetic energy of his motion at the end of the ramp. Make some assumptions and try to calculate the velocity vector of the jumper at the end of the ramp – compare your findings with the gravitational potential energy available and decide if it is at least theoretically possible to perform such a cunning stunt. If so, how much higher should the start point be, above the take-off point?
This week we have almost completed the theory part of the first unit in the Higher Physics course. We have considered uncertainties and how to calculate them before getting down to some real practical physics.
At the end of this first unit, students are required to have completed a small practical investigation into something related to Mechanics and Properties of Matter. This is called “learning outcome 3″ or LO3 for short. We are conducting the practical component of the LO3 this week. Some are investigating the gas laws, others, kinematics.
“The only source of knowledge is experience” Albert Einstein
Einstein’s quote is rubbish, of course. But he has a point – from practical experience, you can really set your knowledge on solid foundations. This is the principle of having a practical element to teaching physics, where such facilities are available.
In the lab, keep your thoughts clearly on the basic principles of scientific investigation that you have already learned: only change one thing at a time, for example, controlling all other factors. Record exactly what you see: for example, the numbers on the voltmeter (indicating pressure indirectly) in the picture should be recorded with the minus sign. If a fire-breathing dragon should walk by your experiment, record the fact and comment on its relevance to the validity of your findings when you come to write up your report.
Your practical activity may be completed as part of a team: some measurements are difficult to do on your own. The report you write on the experiment, however, must be entirely your own work. There is a clear set of performance criteria which your report must meet and you must meet all of them for it to pass as satisfactory. You can find these criteria in the SQA arrangements documents, pages 26-28. There is a simple summary of what your report should include here.
Once you have written the first draft of your LO3 report, before you submit it for marking to your teacher, listen to this podcast tutorial: it takes you through the checklist of essential things your report should have. Enjoy your practical work: here’s another quote to think about, this time from Karl Marx:
“Practice without theory is blind. Theory without practice is sterile.”
I don’t do many book reviews here* but this is a book not to be missed. I bought it in Borders on Saturday after a student recommended it to me – well, to be honest, she was asking me about some of the interesting concepts described in the book.
You can see a short video introduction to the book by the authors over at Amazon.
The flyleaf describes the book as the most accessible, entertaining, and enlightening explanation of the best-known physics equation in the world, as rendered by two of today’s leading scientists. The equation referred to is Einstein’s famous .
The subtitle and why should we care? frames the question asked by Cox’s wife, Gia Milinovich, who describes herself as a science groupie and professional dork. You need not be either of these to appreciate the answer to her question.
The language of the book is very easy-going and the mathematics is kept to an absolute minimum – nothing harder than Pythagoras (and the authors even explain that, in case you have forgotten it). For me, the hook comes in the preface. Don’t skip the preface: it contains some of the most fundamentally important principles of the study of science, for example:
By building a model of space and time, Einstein paved the way for an understanding of how stars shine…
Notice the word model. There’s the greater truth coming:
In science, there are no universal truths, just views of the world that have yet to be shown to be false.
I refer you back to the personal task I set you – and which I have not forgotten, by the way – about the nature of knowledge. The authors of this book are perfectly clear about what knowledge is and what it is not.
Finally, to pique your interest – not just in this brilliant little book, but in the study of physics – let your mind consider this excerpt from chapter 1:
Einstein’s universe is one in which moving clocks tick slowly, moving objects shrink, and we can journey billions of years into the future. It is a universe in which a human lifetime can be stretched almost indefinitely. We could watch the sun die, the earth’s oceans boil away, and our solar system be plunged into perpetual night. We could watch the birth of stars from swirling dust clouds, the formation of planets and maybe the origins of life on new, as yet unformed worlds. Einstein’s universe allows us to journey into the far future, while keeping the doors to the past firmly locked behind us.
I hope you get the chance to read this excellent little book.
This is a worked solution to a problem involving the firing of a missile from a moving helicopter. It analyses motion vectors into orthogonal component vectors, then uses these results to answer the question “where will the missile land?”. The problem as posed was: A helicopter travelling at an angle of 10 up from the horizontal at a speed of 70 fires a missile at 150 . Calculate the horizontal and vertical components of the velocity of the helicopter and the missile. If the helicopter launches the missile at a height of 200 m, how far away does the missile land?
Acceleration is defined as the rate of change of velocity. If we constrain ourselves to thinking about motion in one dimension (direction), this is easily written as , where and are final and initial speeds, respectively. This relationship is easily rearranged to obtain an expression for final speed .
This is the first derivation of three that you should be able to perform. The other two, and are explained by Mr. Spittal in the following video clips:
Part 2 of a worked solution to the following problem:
A golf ball is driven at an angle of 30 degrees to the horizontal at a speed of 12 metres per second. Calculate the horizontal and vertical components of the velocity and thereby the maximum height of the ball, the time of flight and the distance travelled when it lands.
Part 1 of a worked solution to the following problem:
A golf ball is driven at an angle of 30 degrees to the horizontal at a speed of 12 metres per second. Calculate the horizontal and vertical components of the velocity and thereby the maximum height of the ball, the time of flight and the distance travelled when it lands.
.
up from the horizontal at a speed of 70 
fires a missile at 150 
, where 
and 
are final and initial speeds, respectively. This relationship is easily rearranged to obtain an expression for final speed 
.
and 
are explained by Mr. Spittal in the following video clips:
