Author: higher

Dark Matter v Dark Energy

Here are some links for a more in-depth experience of Dark Matter and Dark Energy. (remember Energy ⇒Expansion, Matter ⇒sMaller, or MAtter⇒ Attracts)

http://www.sixtysymbols.com/videos/ed_dark_energy.htm

34 mins interesting video.

http://www.sixtysymbols.com/videos/darkmatter.htm

11 mins on Dark Matter

Brand New Research- could you be a part of this?

https://science.nasa.gov/astrophysics/focus-areas/what-is-dark-energy

https://home.cern/about/physics/dark-matter

http://www.space.com/20930-dark-matter.html
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Nuffield Research Placements 2017 – Dumfries & Galloway Teachers

What an opportunity! Get applying guys! You’ve had some great experiences some of you, lets try to grab you a few more!

Dear all

I am happy to announce that the Online Application System for Nuffield Research Placements 2017 has now opened.

Below is a summary of the application process:

The Nuffield Research Placement Scheme is aimed at the current 5th year students who will be sitting their Highers in 2017 and who are studying any Science, Technology, Engineering and/or Maths (STEM) subjects at that level (e.g. Biology, Chemistry, Physics, Maths, Geography, Computing, Home Economics/Food Technology, Psychology, Music Technology, Product Design, Technological Studies etc.). We are also now starting to place students into Social Science placements where there is an aspect of analysis, statistical investigation and mathematics involved, so it is very wide ranging.

•             Students apply by completing an online application form which can be accessed on the Nuffield Research Placement webpage at http://www.nuffieldresearchplacements.org/

•             The application form has various sections – personal details, education, personal statement, teacher reference, parent consent, bursary application (if appropriate).

•             Once the students register, they insert an email address of the teacher who is to provide them with a reference.  Then once the student submits their application the system automatically initiates an email to that teacher and allows them to log on to the student application, where they can view the various sections and include their reference.

•             After the closing date (Feb 24th 2017), appropriate sections of the application will be forwarded to various supervisors for their consideration – this may then involve an informal interview.

•             If a student and/or teacher has contact details of anyone in local industries/organisations who could offer a placement, they can let us know and include their details on their application. We can then follow this up.

•             If successful, the student agrees start and finishing dates with their supervisor.  The placements normally take place at the end of June, July or early August.  The student will normally be working Mon-Fri (9am-5pm) for 4, 5 or 6 weeks. Students should therefore be made aware that is quite a big commitment.

•             Students will receive travel costs to and from their placement. If they fulfil the criteria as set out in the application form, they may also be eligible for an additional bursary.

•             Successful students are required to submit a report at the end of their placement and are also invited to display their work in poster form at a celebration event in either the Royal College of Surgeons or Royal College of Physicians in Edinburgh (as in a scientific conference). Next year’s event date and venue are still to be confirmed but will most likely be on Friday 1st September 2017.

PLEASE note – there are a limited number of placements available and as such an application does NOT guarantee a Nuffield placement.

The placements help increase confidence and improve key skills including practical, communication, report-writing and presentation skills. It also provides students with excellent experiences & skills to include on CV’s and personal statements. By working with professional scientists and engineers in a real-life environment, the students gain an invaluable insight into a wide variety of careers.

I hope this is of some help to you. If you would like a visit to the school to meet with you and any interested pupils, do just let me know.

More information on the Nuffield Research Placements scheme can be found at http://www.nuffieldfoundation.org/nuffield-research-placements

Please don’t hesitate to get in touch if you have any problems or queries.

The Expanding Universe Practical

A great little practical with washers, that was used as an exam question!

IOP-Elastic-Band-Universe-Student-Activity-InstructionsDownload

Try the following practical

http://www.schoolsobservatory.org.uk/astro/cosmos/uniball

expanding universe school observatory

Expanding Universe Experiment

To understand how the redshift of galaxies is due to the expansion of the Universe, try the following experiment.

You will need the following items:

  1. A round balloon (do not use a long, thin one).
  2. Some coloured stick-on dots (at least 5 different colours).
  3. A piece of string about 50cm long.
  4. A ruler.
  5. A stopwatch or other timer.

Step 1 : Setting Up

You will need to work in teams of at least two, one to blow up and hold the balloon and the other to make the measurements.

Before you start, draw a table for your results like the one below with the colours of your five dots in the 1st column:

Colour of DotFirst Distance D1 in cmSecond Distance D2 in cmChange in Distance        D2 – D1 in cmSpeed v in cm/second
Red    
Green    
Blue    
White    
Yellow    
Time to fully inflate the balloon:        seconds.

Step 2 : Making the Measurements

Putting dots on the small balloon

Blow up the balloon a little bit and hold the “nozzle” closed, but do not tie it up.

Stick your five dots onto the balloon. Try to spread them out over the whole balloon.

stick dots

Each of the dots represents a whole galaxy, with the surface of the balloon being the Universe that they exist in.

Choose one of the dots to be your “home”. You can choose any of them.

Step 3

Use string to measure the distance between two dots

measure dots

While one of you holds the balloon, the other one can use the string to measure the distance from your “home” dot to one of the other dots.

Now measure the string distance with a ruler.

When you have measured the distance, write it down in your table in the D1 column.

Step 4

Measure the distances from the “home” dot to all the other dots as well and fill in that column of the table.

Note: The distance from your “home” dot to itself is zero.

Step 5

Now carefully blow the balloon right up, using the stopwatch to time how long it takes. Write down the time in seconds.

Step 6

Now re-measure all the distances from “home” to all the other dots and write then down in the D2 column of your table. Don’t forget that the distance from your “home” dot to itself is zero.

You now need to work out the speed of each galaxy. Remember that:

Here, the Distance travelled is the difference between D1 and D2, so calculate D2 – D1 for each of our dots and write them in the 4th column on the table.

Step 7

The Time taken is the time to blow the balloon up. Work out the speed V for each dot and put it into the 5th column. Because your “home” dot has not moved, its speed will be zero.

Step 8

We are studying how the speed that galaxies seem to have gets larger for galaxies that are further away.

The best way to see this is to plot a graph showing the distance along the bottom axis and with the speed up the side.

This means that you need to plot a graph with axes like the one below:

speed v distance

Put the points for all your dots on the graph using D2 as the Distance.

Step 9 : What does it all mean ?

Use the ruler to draw a straight line that goes as close to as many of the points as possible (don’t forget the “home” dot!)

Think about the following questions and discuss them:

  • Are the speeds of all the dots the same?
  • If not, do they get faster or slower as they get further from the “home”?
  • What would be different if you had chosen a different “home”?
  • What would have been the same?
  • What do you think this tells you about the way that the Universe expands and the redshift of galaxies?

If you are not sure about some of the questions, can you think of a way changing the experiment to make them easier to answer?

 

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Updated November 2022

Scottish Space School

Hi Guys, I know you can’t all go, and some of you might enjoy yourself so much you might want to repeat so look out for

http://www.strath.ac.uk/engineering/scottishspaceschool/howtoapply/

https://www.facebook.com/ScottishSpaceSchool

The process should begin anytime soon. If you’ve been to London, or not you’ve experienced some amazing things, so let it bring you more excitement.

Go on, you’ve nothing to lose and you may astonish yourself. You are just as worthy, if not more so, than those chosen, so believe in yourself and remember

“The Sky is NOT the limit!”
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The Twin Paradox

Citation for this article:
Markus Pössel, ” The case of the travelling twins ” in: Einstein Online Vol. 04(2010), 1007

The case of the travelling twins- let’s call them Pat and Mike!- pictures to come!

An article by  Markus Pössel

In Einstein’s special theory of relativity, there is no such thing as “time” in the singular. Time passes differently for different observers, depending on the observers’ motion. The prime example is that of the two hypothetical twins: One of them stays at home, on Earth. The other journeys into space in an ultra-fast rocket, nearly as fast as the speed of light, before returning home:

zwillinge

Afterwards, when the twins are reunited on Earth, the travelling twin is markedly younger, compared to her stay-at-home sibling. The exact age difference depends on the details of the journey. For example, it could be that, aboard the space-ship, two years of flight-time have passed – on-board clocks and calendars show that two years have elapsed, and both spaceship and travelling twin have aged by exactly that amount of time. On Earth, however, a whopping 30 years have passed between the spaceship’s departure and its return. Just like all other humans on the planet, the twin on Earth has aged by 30 years during that time. Seeing the two (ex?) twins side by side, the difference is striking.

So far, so strange, but undoubtedly real. Space-travel with speeds close to that of light may be unfathomably far beyond the reach of current technology. But sending elementary particles on round trips in a particle accelerator at 99.99999 percent of light speed is routine. The result is in precise agreement with the predictions of special relativity – the “inner clock” of such a travelling particle runs much slower than that of a particle of the same species that remains at rest.

Turning the tables?

The reason the case of the travelling twins is also known as the “twin problem” or even the “twin paradox” is the following. From the point of view of the twin on Earth, one can explain the age difference by appealing to time dilation a basic concept of special relativity. It involves an observer (more precisely: an inertial observer), for instance an observer that lives on a space station floating through empty space. For such an observer, special relativity predicts the following: For any moving clock, that observer will come to the conclusion that it is running slower than his own. Whether it is a clock on another space station floating past or a clock on an engine-driven rocket, in the time it takes for a second to elapse on the observer’s own clocks, less than a second will have elapsed on the moving clock. This slowdown is true not only for clocks, but for everything that happens on the moving space station or in the flying rocket. All processes taking place on these moving objects will appear slowed down for our observer.

Characteristically, there are situations where time dilation is mutual. For instance, if there are two observers drifting through space, each on his or her own space station, and if those two space stations are in relative motion, then for each observer, the time in the other space station appears to run slower than for himself. (If that already sounds like a paradox to you, you might want to read the spotlight topic The dialectic of relativity.)

With the help of time dilation – often abbreviated to “moving clocks go slower” – one can try to explain what happens to the twins. No wonder the travelling twin ages less! After all, the twin on Earth can invoke time dilation: Moving clocks go slower, and so do the clocks of the moving twin. On these slower-moving clocks – and, by extension, in the whole spaceship – less time passes than on Earth, in other words: when the travelling twin returns, he is younger.

No paradox so far. But why can’t the travelling twin turn the tables on her sibling? After all, motion is relative. Why can’t the twin in the spaceship define herself as being at rest? From that point of view, it would be the Earth that moves away before returning to the spaceship. And if that is so, couldn’t the travelling twin apply time dilation (“moving clocks are slower”) to everyone who remained on Earth? By that argument, shouldn’t it be the humans on Earth that are younger than expected once the twins are reunited? If both twins are on an equal footing, then each one should be allowed to consider herself at rest and invoke time dilation. But in the end, when the twins meet again, only one of them can be right – then, there cannot be any ambiguity: either the one twin is younger, or the other (or, of course, both twins’ arguments are wrong, and they have aged exactly the same). A contradiction – a twin paradox?

The importance of inertial observers

To resolve the contradiction, a closer look at time dilation is needed – in which situations do moving clocks indeed go slower? In the above text, the key criterion was hidden in parentheses: For the dictum “Moving clocks go slower” to hold, you must be an inertial observer. The example of freely floating space stations above gives a flavour of what this qualification means: In an inertial reference frame, all objects are perfectly weightless. For such observers, an object upon which no external forces act (for instance, that is neither pushed nor pulled) either remains at rest or moves with a constant speed along a straight line.

There’s the litmus test for each twin: Is she an inertial observer, and thus entitled to apply the time dilation formula, concluding that moving clocks go slower?

An unfortunate complication: The twin that remains on Earth is no inertial observer. She’s in a gravitational field in which objects fall down instead of remaining at rest. There are two possible ways to proceed. Either one can use Einstein’s theory of gravity, general relativity, and calculate how the gravitational field influences the twin on Earth. The result is that, in the given situation, the Earth’s gravity does not make an appreciable difference. If we ignore Earth’s gravity and treat the twin on Earth as an inertial observer, our results regarding the relative aging of the two twins will be correct, give or take a few fractions of a second. If we choose situations in which the twins eventual age difference is counted in years, gravity will not matter.

Alternatively, one could re-define the situation by having the non-travelling twin wait not on Earth, but in a freely floating space station in deep space, far away from any massive objects. That would definitely make her an inertial observer.

In both cases, the result is that the non-travelling twin has the right to apply the simple time dilation formula, and to conclude that her travelling sibling will be younger when they meet again.

What about the travelling twin? She’s not an inertial observer, either, at least not the whole time. If she simply would simply coast along with constant speed along a straight line, she could never return to Earth (or, in the alternative version, to the other twin’s space-station). In order to return, it is crucial that the travelling twin either come to a stop and accelerate towards Earth or, alternatively, fire her engine to force her spaceship onto a tight curve to point it back towards Earth. In both cases, the travelling twin feels the acceleration – decelerating, her body feels a pull in the direction offlight, re-accelerating, she is pressed into her seat, in flying a turn, she is pulled sideways. Acceleration is inevitable – and while she is accelerating, the travelling twin definitely isn’t an inertial observer. For instance, during a braking phase, objects afloat inside the spaceship’s cabin will not just float or move with constant speed – they will be accelerated toward the front of the spaceship. And in contrast with the twin on Earth, there is no slight redefinition that will do away with these acceleration phases. There’s no way around it: At least for some of the time, the travelling twin isn’t an inertial observer.

Thus the apparent paradox is resolved. The twins are not on an equal footing. The accelerated twin cannot just apply the simple time dilation formula, while her sibling on Earth can. The latter twin’s conclusion that the clocks of the travelling twin run slower, and that the travelling twin is thus younger when they meet again, is valid. (So what role does the acceleration play in this? Find out more in the spotlight topic Twins on the road.)

Further Information

The basics of special relativity – the proper theory to answer all questions about these twins – can be found in Elementary Einstein in the section Special Relativity.

Related Spotlight topics on Einstein-Online an be found in the section Special Relativity.

This is just a draft, I will sort it when my burnt fingers recover!
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Special Relativity & Web-based Research

Communicating Scientific Results

Here is a chance for you to practice some of the skills required for your Investigation. This task gives you some practice to help with your Researching Physics topic. It is to help you look at ways of communicating and think who you are communicating to.Log all the work that you do for this section in your Researching Physics Log Book.

Objective

You will look at the various ways in which findings can be presented, and appreciate the possibility of using other media such as video clips, articles, papers, posters etc.

Learning outcome

You will be more informed about the different ways in which one topic can be presented. You will begin to think about how to present your own work.

Learning activity

You can work independently or in groups. There are three different resources:

  1. A video clip entitled ‘Two postulates’ (http://www.youtube.com/watch?v=WdfnRWGgbd0).

    If you can’t read the file above it has been uploaded here as an MP4 file.

  2. A physicsworld article entitled ‘Slowed Light Breaks Record’

PHYSICS WORLD ARTICLE DECEMBER 2009

3. The paper

‘On Velocities Beyond the Speed of Light c’ (On Velocities beyond the speed of light c.pdf) On Velocities beyond the Speed of Light

You should examine and discuss the three resources. Teachers should point out that even though the physics content may not all be at the students’ level of understanding, it is still possible to take information from it with their level of knowledge. This is emphasised by you completing the work below.

‘Two Postulates’

This clip discusses how to tell if an object is moving or not by way of an animation.

‘Slowed Light Breaks Record’

This is an article published in physicsworld in December 2009. It is not particularly long, although does contain a lot of information.

‘On Velocities Beyond the Speed of Light c’

This paper was published in 1998 from CERN. It has the more traditional scientific report structure and is a good example for you.

After completing the table on the sheet, you should find that all boxes are ticked – highlighting that even though the information is presented in different ways, all the resources contain what the students will have to put into their own reports.

There are many ways to present scientific findings. You might have written a report in the past but universities may ask you to present a poster of your work.

Here we will look at three different ways of presenting findings on special relativity.

On your own or in groups/pairs, have a look at the three examples of how findings on special relativity have been presented.

Copy and complete the table, either with a few notes or a tick or cross, to show if the example meets the criteria.

‘Two Postulates’ ‘Slowed Light Breaks Record’ ‘On Velocities Beyond the Speed of Light’
Is there mention of the objective for the investigation/experiment?
Is there information given on the experiment/s conducted?
Is there mention of the data (perhaps not all) and any analysis of the findings?
Does the article discuss the conclusion for the experiment/investigation?

Now you have looked at the three examples, ask yourself the following questions.

First impressions
  1. Was one resource more eye-catching than the others?
  2. Does one look like it will be easier to read/understand than the others?
  3. Which one looks most credible?
Down to the nitty gritty
  1. Which resource was the most interesting?
  2. Which one was the best presented?
  3. Which gave the most information?
  4. Did you need to understand everything mentioned to gain an understanding of the experiment?

Which format might you consider for your Communicating Physics investigation?

More information on Web-Based Research

Web-Based Research HApr16 A powerpoint presentation showing how to help you find viable websites

Web-Based Research Student Materials Some materials to give you advice on using websites.

Physics Web-Based Research Worksheets Material that you can work through to give you practice at completing web-based tasks.

 

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Homework 2021

LA-Homework-Booklet-2021.docxDownload
LA-Homework-Booklet-2021Download

HW Scholar Revision

Please start completing the Scholar Tests as revision exercises. Passwords and usernames from Mrs Physics.

Try end of section test 2 by the end of February. I think you need to do it in one go or it doesn’t record. So set aside that time.

HOMEWORK PLAN

Found the Question and Answer Files and they are password protected, search for homework answers. Most of the first and last two units are now completed for the LA homework booklet. I will try to complete asap, but it is a slow process.

Due dateWkNotesHomework
25th Jan
1Units, Prefixes & Scientific Notation, UncertaintiesLA Ch1 Revision Ch 3 and Ch4 1 Q GWC Homework 1
1st Feb2Equations of motionGWC Homework 2a, 2b LA Ch 4 any 2 q from pp16-20
8th Feb3Forces Energy & power and CollisionsGWC Homework 3b
LA 1 question from pp21-24, 2 questions from 25-29
15th Feb4Gravitation, Special Relativity & The expanding UniverseGWC homework 7b
LA 2 questions from the Gravitation section, 1 Q from the Expanding Universe section
SQA 2015 Q4 (section 2)
20th Feb5Forces on Charged Particles and Monitoring & measuring A.CGWC Homework 10b
LA pp 45-47, p72
1st Mar6I,V, P & R and CapacitanceLA pp 73, 82,86 + 87 top
8th Mar7Nuclear Reactions and EMF internal resistanceGWC Homework 11a Any 3 questions from the Electrical Sources and Internal Resistance section
15th Mar8Inverse square law and refractionSQA 2015 Q8, LA any 2 questions from the Refraction section. Try 2015 m/c questions as many as you can do in a time of 18 mins
22nd Mar9The Standard Model & Semiconductors and PN junctionsGWC Homework 9a
LA any two from the Standard Model section. LA p90 Q2
29th Mar10Wave particle Duality, Interference and SpectraLA any two questions from the waves particle duality section, any one from the interference section. Pp 66 and 67.
5th Apr11Data skills and OEQSQA 2018 Q13
GWC Homework 8
SQA 2017 Q11, Q15
SQA 2016 Q5

The first link takes you to the Homework Booklet, denoted at LA in the homework table list, that will be used during the course. It is based on the work from Robert Gordon College, so my thanks to all of those who worked on that. There is also work from the notes contained within the 100 pages.

LA Homework Booklet wordDownload
LA Homework Booklet pdfDownload

The second link is for a set of homework questions based on the George Watson’s College Notes, denoted by GWC in the homework table.

GWC Homework Book

Most answers are added to the post above and have been password protected.

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Measurement of acceleration due to gravity

Below are some links and documents for the Researching Physics dealing with measurement of the acceleration due to gravity.

http://practicalphysics.org/measurement-g-using-electronic-timer.html

http://www.practicalphysics.org/acceleration-due-gravity.html

 

 

 

 

 

 

 

 

 

https://revisionworld.com/a2-level-level-revision/physics/fields-0/gravitational-fields-0

The information below is based on the material found from the website above. TBC!

Fields

A field is a region of space where forces are exerted on objects with certain properties. Three types of field are considered:

  • gravitational fields affect anything that has mass
  • electric fields affect anything that has charge
  • magnetic fields affect permanent magnets and electric currents.

These three types of field have many similar properties and some important differences. There are key definitions and concepts that are common to all three types of field.

Gravitational fields

Newton realised that all objects with mass attract each other. This seems surprising, since any two objects placed close together on a desktop do not immediately move together according to Newton’s second law F=ma. The attractive force between them is tiny, and very much smaller than the frictional forces that oppose their motion.

Gravitational attractive forces between two objects only affect their motion when at least one of the objects is very massive. This explains why we are aware of the force that attracts us and other objects towards the Earth – the Earth is very massive. The mass of the Earth is about 6 × 1024 kg.

The diagram represents the Earth’s gravitational field.

The lines show the direction of the force that acts on a mass that is within the field.

This diagram shows that:

  • gravitational forces are always attractive – the Earth cannot repel any objects
  • the Earth’s gravitational pull acts towards the centre of the Earth
  • the Earth’s gravitational field is radial; the field lines become less concentrated with increasing distance from the Earth.

The force exerted on an object in a gravitational field depends on its position. The less concentrated the field lines, the smaller the force. If the gravitational field strength at any point is known, then the size of the force can be calculated.

The gravitational field strength, g, at any point in a gravitational field is the force per unit mass at that point

g=F/m

Close to the Earth g has the value of 9.8 Nkg-1

Gravitational field strength is a vector quantity, its direction is towards the object that causes the field.

Universal gravitation

Newton concluded, during his work, that the gravitational attractive force that exists between any two masses:

  • is proportional to each of the masses
  • is inversely proportional to the square of their distances apart.

Newton’s law of gravitation describes the gravitational force between two points. It can be written as

F=(GMm)/r2

Where

G is the universal gravitational constant and is equal to 6.67 × 10-11 N m2 kg-2  .   M and m are the magnitude of the masses and r is the separation between  the centre of the masses.

A point mass is one that has a radial field, like the Earth as shown in the diagram above.

Although the Earth is a large object, on the scale of the Universe it can be considered to be a point mass. The gravitational field strength at its centre is zero, since attractive forces pull equally in all directions. Beyond the surface of the Earth, the gravitational force on an object decreases with increasing distance. When the distance is measured from the centre of the Earth, the size of the force follows an inverse square law; doubling the distance from the centre of the Earth decreases the force to one quarter of the original value.  The two objects attract each other with equal sized forces and act in opposite directions. The variation of g with distance from the surface of the Earth is shown in the diagram.

g and G 

Newton’s law of gravitation can be used to work out the value of the force between any two objects. It can also be used to calculate the strength of the gravitational field due to a spherical mass such as the Earth or the Sun.

F=(GMm)/r2

As the value of F is also the weight then we can equate these two quantities, so that g not only equals W/m but also g=(GM)/r2 as below

Gravitational field strength is a property of any point in a field. It can be given a value whether or not a mass is placed at that point. Like gravitational force, beyond the surface of the Earth the value of g follows an inverse square law.

Because the inverse square law applies to values of g when the distance is measured from the centre of the Earth, there is little change in its value close to the Earth’s surface. Even when flying in an aircraft at a height of 10 000 m, the change in distance from the centre of the Earth is minimal, so there is no noticeable change in g. The radius of the Earth is about 6.4 × 106 m, so you would have to go much higher than aircraft-flying height for g to change by 1%.

The same symbol g is used to represent:

  • gravitational field strength
  • free-fall acceleration.

These are not two separate quantities, but two different names for the same quantity. Gravitational field strength, g, is defined as the force per unit mass, g = F/m.

From Newton’s second law and the definition of the newton, free-fall acceleration, g, is also equal to the gravitational force per unit mass. The units of gravitational field strength, N kg–1, and free-fall acceleration, m s–2, are also equivalent.

 

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