Here are the solutions to the dynamics and space past papers questions.
Nat5 dynamics & space questions
Some of you asked for revision questions ahead of the unit assessment. Down load these problems from older past papers. I will add a secoond post with the answers shortly.
Hubble discovers our universe is expanding
In the 1920s, Edwin Hubble had access to the Hooker telescope on Mount Wilson, Los Angeles. This was the largest telescope in the world at that time. His first breakthrough was the discovery of a cepheid variable star in the Andromeda nebula. This enabled him to calculate the distance to Andromeda and he quickly realised this was not a nebula but a galaxy outside the Milky Way.
This video follows his work.
Hubble – nebulae or galaxies? from mr mackenzie on Vimeo.
Hubble then turned his attention to other galaxies, looking for cepheid variable stars that would allow him to determine their distances from the Milky Way. He used redshift to calculate their recession velocity and plotted a graph against distance.
He found that the recession velocity (v) was directly proportional to distance (d). We can express this relationship as
where is the Hubble constant. Astronomers agree that the current value of the constant is
.
Since this is a SQA course, we need to convert into SI units – giving
In this video, Professor Jim Al-Khalili looks at Hubble’s work on the expanding universe.
Hubble’s discovery of the expanding universe from mr mackenzie on Vimeo.
Although he was American, Edwin Hubble transformed himself into a tea drinking, pipe smoking, tweed wearing Englishman during his time as a Rhodes Scholar at Oxford. He probably wouldn’t approve of this last video.
Unfortunately, astronomers were not eligible for the Nobel Prize for Physics. The rules have now been changed.
temperature, colour and line spectra
We’ve been looking at how the temperature of an object can affect it’s appearance. The attached handout recaps on our work in class and provides some examples of line spectra.
redshift
more redshift
and Yoker Uni’s video about Doppler and stuff
While redshift can be used to tell us about the recession velocity of (non relativistic) galaxies, we also need to find a way to measure the distance to these galaxies. Astronomers have two main methods to measure these distances; parallax (more parallax here) and cepheid variable stars – there’s a Khan Academy video on cepheid variable stars.
using redshift to map the expanding universe from mr mackenzie on Vimeo.
special relativity
Special relativity is tricky get get your head round. Let’s start with a video about the speed of light.
This video follows Einstein’s thought process as he worked through his special theory of relativity.
time dilation
A Tale of Two Twins from Oliver Luo on Vimeo.
another take on special relativity and the twins paradox
…and the Glesga Physics version
length contraction
This video has helpful examples to explain length contraction.
Sometimes it’s easier to imagine we’re a stationary observer watching a fast moving object go whizzing past. For other situations, it’s better to put yourself into the same frame of reference as the moving object, so that everything else appears to be moving quickly, while you sit still. The muon example in this video shows how an alternative perspective can work to our advantage in Special Relativity.
Another way to think about this alternative frame of reference is that it’s hard to measure distances when you yourself are moving really quickly. Think about it, you’d get tangled up in your measuring tape like an Andrex puppy.
image: trotonline.co.uk
It would be far easier to imagine you’re the one sitting still and all the objects are moving relative to your position, as if your train is stationary and it’s everything outside that’s moving. That keeps everything nice and tidy – including your measuring tape. Got to love Einstein’s postulates of special relativity.
image: mirror.co.uk
changing state – latent heat of fusion/vaporisation
Before the holidays, we performed a set of experiments to determine the latent heat of fusion and latent heat of vaporisation of water. Next week, we’ll review that work and think about possible reasons why our results were not closer to the “book” values.
The attached pdf provides a summary of the topic.
National 5 – Satellites
We’ve started looking at telescopes and this BBC programme from 2 years ago featured the replacement for Hubble, the James Webb Space Telescope. The presenter, Maggie Aderin Pocock now hosts The Sky at Night on BBC4.
Please take some time to watch both parts of the film. Maggie covers the basic idea of satellites, how we achieve geostationary orbit, looks at examples of Earth observation and the manufacture of the James Webb’s massive 6.5m mirror. In part 1, around 17 minutes in, you’ll see satellite footage over the Highlands, can’t quite see Thurso though.
Satellites-part1 from mr mackenzie on Vimeo.
Satellites-part2 from mr mackenzie on Vimeo.
If you want to download a copy of the video to watch later, use the download link below. Please be patient, the file is about 660MB in size.
extra nat5 revision materials
You can also use these notes to prepare for the test on Monday. The test will cover everything up to page 46 in the attached file, but you can skip pages 39 & 40 on Newton’s third law.
Thanks to Mr Noble for sharing his notes.
Nat5 revision materials D&S unit
Use these materials to help you prepare for the assessment at the start of next week. Studying up to page 7 of the attached file will cover the topics in the test.