National 5 – fizzics Sinclair Mackenzie

We’ve been looking at forces for the past two weeks. Here are some notes and videos to help you learn more about this topic.
Newton’s 1st Law

animation showing effects of air resistance
Friction: here are 3 clips about friction from the BBC programme Bang goes the Theory
//www.youtube.com/watch?v=qhpXnGaYmdA
//www.youtube.com/watch?v=XNOEP1XIFiM

and look what happens when cold weather removes the friction that helps you to control your car!
//www.youtube.com/watch?v=7MPRmOUxRMY
Here are some videos on balanced and unbalanced forces affecting the motion of objects.  The first clip examines the forces on a cyclist as she cycles round a velodrome.
//www.youtube.com/watch?v=WoTQDrzCqb0
The second clip looks at the way skydivers use forces to land safely.

//www.youtube.com/watch?v=io-6uYOQK6A


Newton’s 2nd law

Newton’s 3rd law

I’ve written a blog post on Newton’s third law during a rocket launch that shows Newton’s 3rd law very clearly.  There’s also a follow-up post on Newton’s third law with footage of the Apollo 11 rockets destroying the launch pad.
If you’ve read all that stuff on forces, take a break to watch the Glesga Physics Newton’s Laws video
httpv://www.youtube.com/watch?v=OCnLcq3LBEg

X-rays are a form of electromagnetic radiation.  They have a much higher frequency than visible light or ultraviolet.  The diagram below, taken from Wikipedia, shows where x-rays sit in the electromagnetic spectrum. image by Materialscientist Wilhelm Röntgen discovered x-rays and the image below is the first x-ray image ever taken.  It shows Mrs. Röntgen’s hand and wedding ring.  ... Read more

We started looking at half-life today.  The attached file walks you through different types of half-life problem.  There are some questions for you to try along they way.  The answers are at the end, please don’t cheat!

X-rays are a form of electromagnetic radiation.  They have a much higher frequency than visible light or ultraviolet.  The diagram below, taken from Wikipedia, shows where x-rays sit in the electromagnetic spectrum.

image by Materialscientist
Wilhelm Röntgen discovered x-rays and the image below is the first x-ray image ever taken.  It shows Mrs. Röntgen’s hand and wedding ring.  The x-ray source used by Röntgen was quite weak, so his wife had to hold her hand still for about 15 minutes to expose the film.  Can you imagine waiting that long nowadays?

This was the first time anyone had seen inside a human body without cutting it open.  Poor Mrs. Röntgen was so alarmed by the sight of the image made by her husband that she cried out “I have seen my death!” Or, since she was in Germany, it might have been
“Ich habe meinen Tod gesehen!”
that she actually said.
Röntgen continued to work on x-rays until he was able to produce better images. The x-ray below was taken about a year after the first x-ray and you can see the improvements in quality.

Notice that these early x-rays are the opposite of what we would expect to see today. They show dark bones on a lighter background while we are used to seeing white bones on a dark background, such as the x-ray shown below.  The difference is due to the processing the film has received after being exposed to x-rays.
In hospitals, x-rays expose a film which is then developed and viewed with bright light.  X-rays are able to travel through soft body tissue and the film behind receives a large exposure.  The x-rays darken the film. More dense structures such as bone, metal fillings in teeth, artificial hip/knee joints, etc. block the path of x-rays and prevent them from reaching the film.  Unexposed regions of the film remain light in colour.
Röntgen’s x-ray films would have involved additional processing steps.  The exposed films were developed and used to create a positive.  In creating a positive, light areas become dark and dark areas become light.  So the light and dark areas in Röntgen’s x-rays are the opposite of what we see today.  Our modern method makes it easier to detect issues in the bones as they are the lighter areas.
Röntgen was awarded the first ever Nobel Prize for Physics in 1901 for his pioneering work in this field of physics.
 

I have attached a recording of a short BBC radio programme about the first x-ray and what people in the Victorian era thought of these new images.  Click on the player at the end of this post or listen to it in iTunes.