We also discussed ways of cooling stuff down and trying to make liquid nitrogen...
Cover Lesson
Classwork
I'm away with Mr H at a physics teaching event today.
Please continue your revision for your external/internal exams.
If you have not yet used it you can try this specimen paper - questions 2,4,5,6,10,13,17,19,20,21,22,23,24,25,26 are relevant to what we have studied. The markscheme is online.
You might want to take the opportunity to do some research and find out stuff like the value of g in London and also maybe the Young modulus of copper to compare with your experimental result. You need to be able to "carry out research and report findings; sources of information are cited together with supporting planning and conclusions".
If you want to have a go at the uncertainty analysis for the Young modulus experiment then please give it a go - we will go over this next lesson.
NEWSFLASH the rubber band finally broke last week! Nobody saw it happen though :(
HARD Questions
Classwork
We did some work on SI Base Units. If you missed the lesson I would STRONGLY ADVISE you to work through these and check your answers.
We then did some HARD questions around uncertainty and practicals.
Again, if you missed the lesson, please go through these as part of your revision - the answers are in the pdf.
Homework
Officially there is no homework, but if you want to practise solving quadratic equations try this site (though not all the problems will involve solving a quadratic).
Note that they give you the quadratic formula on the formula sheet.
Multiple Choice Questions
Classwork
We practised some multiple choice questions. These are quite tricky and take a bit of getting used to.
It's important that we do some more of them, as they come up in the AS and the A Level exams.
There are lots of questions for revision here that are broken down into chapters from the book. There is also a big pdf with LOADS of past paper questions & answers.
Next lesson we will go over uncertainty, and also try to look at some 6 mark questions.
We should also do some practice with units and conversion to SI base units.
Homework
No homework this week!
Revision
Classwork
We went over key problems from specimen paper 1, and also discussed how compression can have different effects depending on the shape of the sample (e.g. it can crush or buckle).
We did some pen races, and I introduced a very tricky problem about chocolate. Let me know if you work out a strategy.
Homework
If you are feeling extra keen you could make your own bingo here or your own kahoot here.
Going over test
Classwork
We went over the test, and I demonstrated single and double slit diffraction patterns again.
We discussed optical fibres for communication, and whether they also need an opaque layer over the cladding to stop rays that escape from entering other fibres.
Rays can escape either at the start of the fibre (where rays enter with a big range of angles) or anywhere along the fibre if it is bent sharply.
I did a demonstration like this and we tried various adaptations to get a good stream of water, and to see the reflected path within the water stream.
Do these and hand in when you can, Thursday morning at the latest. I will do my best to mark them before the lesson on Friday.
Test
Classwork
We observed that the rubber band has crept quite a long way since the experiment was started, and seems to have been speeding up recently.
I also mentioned the pitch drop experiment which has been going on for quite some time...
We played 'pen races' which is a game I invented last year. I will try to make a website at some point that overlays different race tracks.
There is lots of interesting psychology research that could be done with pen races - e.g. effects of age, practice, dominant/non dominant hand, correlation with other skills, relative difficulty of different camera angles/inversions...
If you are interested in this sort of thing then talk to Miss Baker as this is her area of expertise.
Also, we did the test.
Homework
No homework.
Revision
Classwork
I briefly finished explaining how the choice of cladding material can reduce multipath dispersion.
It's probably worth answering the last two questions on P209 and checking your answers using the markscheme from the lesson.
Revise for test on Friday.
Optical Fibres
Classwork
We looked at how rainbows formed, and found that there are lots of different types of rainbows.
We looked in detail at opitcal fibres.
I made an optical fibre to demonstrate how flexible they are, and to show light travelling elong it, even when it was bent.
We made notes on cladding, transferring information down fibres, dispersion, and coherent and incoherent bundles.
We have now finished the syllabus. Yay.
Homework
Revise for a test next Friday on Chapter 13.
We will have some time next Tuesday for revision in the lesson if you want to go over anything.
Total internal reflection
Classwork
You traced the path of a ray through an optical fibre. Remember that light refracts when it enters and leaves the fibre.
We discuessed uses for optical fibres, and wider uses of TIR. You might want to look for a video that explains how you see rainbows - this is a nice example of TIR.
We made notes on total internal reflection and the critical angle, and derived the formula for the critical angle for a boundary between two transparent media.
We considered situations when TIR could or could not occur.
Homework
Answer Q1-3 on P195 and hand in tomorrow morning beofre registration.
More Refraction
Classwork
You did a tricky starter question about light passing through a hollow triangular shape, then repeated with the shape filled with water.
I then demonstrated this, and we saw how sensitive the deflection of the light was to the refractive index of the water by mixing hot water with cold water. It looked cool.
You then did a practical to investigate refraction and total internal reflection in a semicircular perspex block.
Homework
Calculate sin(i) and sin(r) for each row of your table.
Plot a suitable graph so that the gradient gives you the refractive index of the perspex.
We made brief notes on the speed of light, refractive index, and the refraction formula.
Homework
Answer the questions on P189 and hand in on Thursday morning at the latest.
Last of Diffraction Gratings
Classwork
We went over path difference, phase difference, maximum order, and why the fringes produced by a diffraction grating are sharp with big gaps between them.
We went through the questions, and I demonstrated the pattern produced by a narrow beam of white light.
You started a practical to find the line density of a diffraction grating.
Homework
You should have a rough idea of the line density from today's lesson. Do some research and think about how you can improve this result, ideally using a graph.
Make notes on 'maximum order' and 'missing orders' using a video I am about to make.
Diffraction patterns, diffraction grating
Classwork
We went over the difference between the single and double slit diffraction pattern.
We briefly went over the two slit pattern with white light - I will try to demonstrate this next lesson.
We looked at the experimental setup to observe a two slit diffraction pattern from a monochromatic but incoherent light source.
I demonstrated the diffraction pattern from a diffraction grating. You will use a grating for a required practical next week.
Homework
Use this video and P205-6 to make notes on diffraction gratings and the diffraction grating formula.
By the way, I never mentioned that he is the same Young of Young Modulus fame, and he was a bit of an all-round legend. Read more here.
You did the double slit practical with a laser, and deduced the wavelength of the laser. We will improve on this measurement using a similar technique next week.
I demonstrated a single slit diffraction pattern by covering one of the double slits.
You started, and many of you finished, the questions on P198.
Homework
Finish the questions on P198 and check your answers in the back of the book.
Watch this video to find out about double slit diffraction of white light. The pattern is right near the end at around 7:08.
Make notes on white light fringes using P201.
Remind yourself of the single slit pattern you saw today with this video. No need to watch the whole thing.
Make some brief notes on the single slit diffraction pattern, and how it differs from a double slit pattern. P202 and the first half of P203 will help.
We went out to the field to experience two source sound interference, and I also tried to do it with water ripples on the pond with some success. This video has a great demonstration with water ripples.
We started to make notes on two source interference, and defined coherence.
Homework
Watch this demonstration of Young's double slit experiment. You will do this experiment next lesson.
Use P196-7 (stop when you get to the "Theory of the double slit equation") and this video to make notes on the experiment.
Make sure you have a clear, labelled diagram of the experimental setup, and you are clear about the definition of the slit width and fringe separation.
PLEASE USE THE SYMBOLS AS THEY ARE IN THE TEXTBOOK - the video I linked to is good, but he uses different symbols for things, so don't use his ones.
YM Prac
Classwork
We went over the test you did on chapter 11.
You did required practical #4 - finding the Young modulus of copper.
We agreed to do a test on Chapter 11 on Friday 12th Feb.
By today, the rubber band has extended by 34mm. It vibrates at a frequency of 116Hz. We will continue to monitor this over time.
The formula for the frequency of vibration is here - can you work out from that whether the pitch will increase or decrease if it extends further???
Homework
Complete the past paper questions and check your answers using this markscheme.
Investigating stress and strain
Classwork
I demonstrated Searle's apparatus, and you made notes on the key features.
You then conducted a somewhat laborious expreiment to enable you to plot a stress-strain curve for copper.
I also set up an experiment to investigate creep in rubber. As of 2:41pm the rubber has extended by around 14mm.
Homework
Plot a graph of stress against strain.
Find the initial gradient of the graph.
Hand in on Monday morning before registration.
TAKE VERY GOOD CARE WITH UNITS THROUGHOUT.
Breaking Stress
Classwork
We did a quick question on combining springs.
I gave you some feedback on the HW and some common errors to avoid.
You did an experiment to find the breaking stress of copper.
You then predicted the breaking force for a thicker copper wire, and I tried to test this at the end (it didn't suppot my weight...).
Homework
Watch this video which puts the HW in the context of the lesson.
Use P168-9 to make notes on stress-strain graphs, the Young Modulus, and brittle/ductile materials. You may find this video useful.
Answer Q1-2 on P169 and check your answers in the back of the book.
Don't make notes on Searle's apparatus (Figure 2) - I will demonstrate this next lesson.
Watch some of this video which shows a real stress-strain test. You don't need to make notes on this or watch the whole thing - it's just to show you how it's really done.
NOTE: when we do the experiment, we will vary the force and measure the length. In the video, they vary the length and measure the force.
Springs
Classwork
We went over the definitions you found for your HW.
We made notes on Hooke's law & the energy stored in a spring.
You inviestigated combinations of springs in series and parallel, and I gave you the formulae to calculate the effective spring constant of a combination of springs.
You started the questions on P166.
Homework
Complete Q1-3 (inclusive) on P166 and check your answers in the back of the book.
Make notes on stress and strain, using the video and P167. These notes will be quite brief.
Calculate the stress when:
a 50N weight is hung from a rod of cross-sectional area 10-4m2
a 2.5kg mass is hung from a round wire of radius 1mm
a 50g mass is hung from a hair of diameter 0.1mm
Calculate the strain when:
a 1.5m long rod extends by 0.02m
A wire of length 200cm extends to a length of 208cm
a hair of length 20cm extends by 4mm
Hand in your stress/strain notes and answers to the questions above on Monday morning before registration.
PS the video I linked to is NOT by the guy I referred to in the lesson!
Extending rubber
Classwork
We went through the test from last week. As an estimate I would say that 73% would correspond to an A,and 84% would be an A*.
You did a practical to investigate loading and unloading of a rubber band.
Homework
Finish your graph with F on the y-axis and ΔL on the x-axis. Your graph should be somewhat similar to Figure 2 on P171 (but there may be some differences).
Use P170-171, the glossary, and other sources if necessaary to define (in the context of a spring/wire/rubber band/whatever):
the 'limit of proportionality'
the 'elastic limit'
elastic deformation
plastic deformation
what the area between the curve and the x-axis on a force-extension graph represents
Hand your graph in tomorrow morning before registration, and bring your definitions to next lesson.
Test
Classwork
You did the test.
Homework
No homework.
P=Fv, Renewables
Classwork
We looked at the derivation and use of the formula P = Fv (see P154).
We discussed renewable energy, and did some rough calculations to estimate the average power output of a tidal power system.
Homework
Revise for test on Friday.
Power and Efficiency
Classwork
We did a starter question about energy transfers.
I went over some important information about dropping Physics.
We set a date for a test on Chapters 9-10 and Momentum for Friday 15th January.
I demonstrated an electric crane made from lego. We calculated the total power input, the useful power output, and the efficiency.
Homework
Revise for test next week.
Answer the questions on P154 and check your answers in the back of the book.
You can hand in at any time if you want me to check anything.
Rockets, work, rifles
Classwork
We went over the rockets sheet in detail - hopefully that makes more sense now.
We also went over the new formula for work done and the formulae for the energy stored in a spring.
Then we did a practical to work out the speed of an air rifle pellet.
UNFORTUNATELY THE POWER CUT MEANT THE DATA FROM THE LESSON WERE LOST :( so this is from memory....
Mass of ten airgun pellets was 7g.
Mass of trolley was 595g.
Time for trolley (and embedded pellet) to travel 100cm was about 6 seconds (can't remember exactly).
Homework
Work out:
a) the momentum of the trolley (and embedded pellet) after the pellet hit it
In particular note the new formula: W = F d cos(θ)
Also note the work done stretching a spring is HALF F x Δl
This makes sense when you consider the area under the force-displacement graph.
Homework
Answer the questions on P150. Check your answers in the back of the book and hand in on Wednesday morning before registration.
Catch up work - momentum and rockets
Classwork
Please collect your HW from my locker and try to correct any mistakes before Tuesday's lesson.
Read the bottom part of P5 (from where it says 'In general') and the top part of P6 (up to where it says 'Force-time graphs') of the handout and make notes. This applies when something like a rocket ejects stuff at a constant velocity relative to the rocket, and the rocket loses mass at a constant rate.
v is the relavitve velocity that the stuff gets ejected at
Δm/Δt is the 'rate of change of mass' = i.e. how many kilograms of mass are lost per second
The first half of this video does an example calculation (he uses dm/dt instead of Δm/Δt but don't worry about that).
Print off these questions about rockets and answer them. Some of these questions are QUITE HARD, so just do what you can and don't spend ages on them.
Hand the sheet in on Monday morning before registration.
Collisions & impulse
Classwork
We did a question about a collision that was inelastic, then considered what would happen if it was elastic.
We then tested this with some trolleys.
We went over the questions on P15.
You started Q1-3 on P10.
Homework
Watch this video about golf balls if you like. Turns out they don't use wound rubber any more, but one of the old ones does.
Answer these questions and hand in tomorrow morning before registration.
Work to catch up on
Classwork
Answer the questions on P15 about elastic and inelastic collisions - they should be ok as we have already made notes on this.
Answer the questions on P13 about collisions. You have done calculations like this at CGSE so they should be ok. Just remember you need to be really careful with direction and sign.
That should do it - I will try to post the answers on here since you don't have them in the back of your booklet to check.
Bring your work to next lesson.
Explosions, elastic & inelastic collisions
Classwork
I gave you some tips on how to correct HW mistakes.
I will post the work for Friday's lesson that you will miss on here soon.
Test, momentum
Classwork
We went through the HW, and the issues people had with the lift question and the slope question.
We went through the test from last half term. If you want some more questions to practise from this topic, or you need to go through some stuff, let me know.
I am very busy for the next two weeks with mock Oxbridge interviews, but I can give you some extra questions for now.
Then we started to look at momentum, and we recapped on some basic concepts from GCSE.
Homework
Answer the questions on P13 and hand in on Monday before registration. No late HW please!
We looked at terminal velocity in the context of a skydiver and a car raching top speed.
We did an experiment to show that an empty water bottle and a full water bottle fall at a very similar rate, but if you drip them from high enough the full bottle falls faster.
I also demonstrated some ball bearings reaching terminal velocity in a viscous liquid, and we considered why the bigger ball fell faster (and why bigger bubbles rose faster).
Homework
Revise for test next Friday on Chapter 7 and Chapter 8.
Make sure you have correctly calculated t (should be around 0.4s) and the velocity it leaves the table at (should be about 2m/s). If necessary go through your calculations again.
Homework
...and also Period 4
Watch this video which I just made that should explain how to calculate the maximum possible speed from today's practical. Then consider why the actual speed was less than the maximum possible speed.
Do some indepentet work on Chapter 9. There is very little new material here so we can move quickly. Here's what you need to cover - if you have suitable notes from GCSE then there's no need to write them out again.
Make sure you are happy with Newton's Second Law by answering the questions on P134 - check your answers in the back of the book. These are pretty straightforward.
Check your understanding of terminal velocity. Watch this video from 3:05 onwards and use P138-9 of the textbook.
Next lesson we'll do some questions about Newton's First and Second Laws, and look at terminal velocity in more detail.
Horizontal Projection
Classwork
I gave out the markscheme for Q1-4 P130, and you marked each other's work.
We have now pretty much finished chapters 8 and 9, so revise for the text next week.
Check your answers to the questions on P127, and repeat any that you have got wrong using the method we used today.
Independent Work
Classwork
NOTE: You can swap the classwork and homework if you can't get on a computer during the lesson.
Watch this video which introduces horizontal projectile motion. Then watch this demonstration of it happening in the real world.
Then watch this video which gives an example of working through to the solution of a problem - though I would encourage you to always lay out your method is the "suvat" way for the vertical motion. There is no need to "suvat" the horizontal motion since there is no horizontal acceleration - just use velocity = displacement/time for the horizontal part.
Use P126-7 and these videos to make notes on horizontal projection.
Now answer the questions on P127 and check your answers in the back of the book.
Homework
Answer Q1-4 on P130 and bring to next lesson.
Measuring g by free-fall
Classwork
We did a practical to measure g by free-fall.
You recorded this in your lab books.
Homework
Finish your practical write-up. Make sure you have:
put the date on each page of your work
calculated the gradient
worked out g based on your gradient
included a diagram of the apparatus, showing the height you measured
Also write a sentence or two that concludes & evaluates your experiment. What did you find, how does it compare to the expected value, and what reasons could there be for any discrepancy between your measurement and the expected value of g.
Acceleration due to gravity
Classwork
We estimated g by timing a ball falling over a known distance.
We considered the impact of increasing and decreasing the height on the quality of the measurement.
We looked at percentage uncertainty.
You read P119-120 and answered the questions on P121. Check your answers in the back of the book
Homework
Make notes on projectile motion. Use P126-7 and this video.
Next lesson you will find g by experiment (using a more sophisticated method that I demonstrated today) and we will start doing some projectile motion problems.
suvat
Classwork
I showed you how to solve suvat problems, and we did a few examples.
We did a practical to investigate the acceleration of a marble rolling down a ramp at different angles.
I marked your answers to the questions on P110-111 and gave out the markscheme.
Homework
Correct your answers to P110-111, using the markscheme where necessary.
Finish your graph.
Next lesson we will move onto suvat problems with vertical motion, which can be harder.
Watch this video to see how a harder question is approached, and see how important it is to be careful with the sign (+ or -) uf your numbers.
In physics we will almost always consider upwards to be positive.
Cover Lesson - Independent Work
Classwork
The classwork is to recap on stuff we did on moments.
Answer Q4-8 on P108-109, drawing diagrams for each question and making your working clear. Check your answers in the back of the book.
Answer Q2-4 on P110-111. You will need a bit of graph paper for Q2. The answers to these are not in the back of the book - we will go through them next lesson.
Homework
You should be familiar with the formula a = (v-u)/t from GCSE. Answer Q1-4 on P115, which use this formula, and check your answers in the back of the book.
Bring all this to tomorrow's lesson - I won't be able to mark any of it before the lesson.
Graphs of Motion
Classwork
We went through the HW, and some subtle points about stability and the force needed to tilt something.
We did a moments question that invovled working out the perpendicular distance.
We recapped in detail on graphs of motion - if you missed the lesson then you really need to go over this before next lesson.
Homework
The "suvat" equations are a set of equations that can be used to solve problems when an object is accelerating uniformly.
Watch this video and read P116-8 to find out what the suvat equations are, and how they are derived.
You don't need to be able to derive them, but it's very nice to see how they can be found by looking at graphs and using your existing knowledge.
Bring your notes to next lesson, when we will start to use the suvat equations to solve problems.
We made some notes on couples and tilting, and started an experiment on tilting.
Homework
Add to your notes on 'tilting' to also cover toppling. Use P102 of the textbook and the video from last Friday's HW. This should be very short as you did it at GCSE and have already watched the video.
Answer the questions on P103 and hand in tomorrow morning before registration.
Watch and make notes on this video about 'perpendicular distance'. We will do some problems next lesson.
Moments - two support problems
Classwork
We made notes on two support problems and did some examples.
We started the questions on P100 and went through Q1&2.
Homework
Finish the questions on P100.
Read P100-102 inclusive. No need to make notes.
Watch this video about centre of mass and stability. Again, no need to make notes.
Bring everything to next lesson.
Moments
Classwork
We finished off forces in equilibrium by answering Q1-5 on P108.
You calculated the weight (and mass) of a metre ruler by balancing it off-centre (see P98 of AQA).
Homework
Answer Q1-4 on P98 and hand in tomorrow morning before registration.
If you haven't done moments before, then watch this video and read and make notes on P97-98. You can hand the questions in later if you can't manage them by tormorrow.
Three forces in equilibrium
Classwork
We went through the HW & covered 'equilibrium' in more detail.
We did the experiment shown in Figuire 5 of P95 of the AQA textbook.
We looked at two different strategies to find the unknown force when there are three forces in equilibrium (see P94-96).
Homework
Answer Q1-4 on P96 of AQA and hand in before registration on Monday morning.
