## Graphs, Gravitation

### Classwork

- We did some practice of getting stuff from log log graphs.
- I gave out this set of past paper questions about gravitation.
### Homework

- Continue your revision.

## Feedback

### Classwork

- We went through Section A Part 2 and Section B of the mock.
- We looked at a few other papers to practise working out the units for table headings and gradients etc.
- We also looked at the meaning of the gradient and the y intercept of a log log graph.
### Homework

- Continue your revision.

## EMPA Mock

### Classwork

- Those of you who had not already done the Part B yet did it today.
- We will go through it in tomorrow's lesson.
### Homework

- Continue your revision.

## Past paper questions + EMPA feedback Classwork

- We did some multiple choice past paper questions on further mechanics and went through this.
- We went through Section A Task 1 of the EMPA mock.
### Homework

- If you haven't done it yet, revise for EMPA Part B Mock on Monday.

## Catch Up

### Classwork

- I gave back the Unit 4 mock - will print the markscheme for you tomorrow.
- People caught up on missed papers + a few got ahead with the mock EMPA section B.
- The rest of you will complete Section B after the holidays.
### Homework

- Revise. Here are lots of past paper questions and here are the answers.
- The answers to the end of chapter questions in the textbook are here.

## Unit 2 Mock

### Classwork

- We did the mock.
### Homework

- No homework.

## EMPA Mock

### Classwork

- We did Section A Part 1 of the EMPA Mock.
### Homework

- Revise for mock next week.
- Please arrive promptly to the lesson on Monday or you will lose time for the mock.

## EMPA Mock

### Classwork

- We did Section A Part 2 of the EMPA Mock.
- We will do Section A Part 1 tomorrow.
### Homework

- Revise for mock next week.
- Please arrive promptly to the lesson on Monday or you will lose time for the mock.

## Generators, flux linkage and emf

### Classwork

- We went through the EMPA Part B and the questions from the HW. We derived numerous formulae for the flux linkage and emf for a rotating coil. We did a past paper question on flux and flux linkage. We discussed back emf in a motor (the start of this video gives a very simple explanation) and I started to discuss back emf in a transformer under no load - more on this later.
### Homework

- Print and complete these past paper questions and hand in before registration on Thurs. Revise for mock on Monday 23rd.
- Next week we will a mock EMPA practical and try to wrap up a few last things from the syllabus (three phase generator and eddy currents).

## EMPA Part B

### Classwork

- I will not be here on Monday. Please make sure you bring your Part A from the EMPA practice we did a few weeks ago.
- Collect the Part B from Lab 12 and complete it. Hand in to my pigeon hole when you are finished.
- DO NOT CHEAT AND LOOK UP THE MARKSCHEME - try to think about the answers carefully.
- Also collect your HW which I have marked and do any corrections. I have left some sample answers in Lab 12.
### Homework

- Watch this video about generators. If you don't do maths you can skip the differention bits, but watch the start (which shows the origin of the cosθ term) and the end (which shows the maximum value of emf).
- Make notes on the video and P127 (but not P128-9) - most importantly the formulae
NΦ = BANcosθ ε = ε _{0}sin(2πft) - Answer Q1-3 on P129 and hand in before reg on Tuesday.

## Faraday's Law

### Classwork

- We went through the HW sheet together.
- We made some notes on Faraday's Law and did some questions on P126.
### Homework

- Read P130-132 about transformers. As far as I know, you don't need to be able to do the derivation on P130.
- You can watch this video if you like.
- Make notes on these pages (should be quick - apart from the derivation it is VERY similar to what you have done at GCSE).
- Answer Q1-3 on P132 and hand in on Thursday morning.

## Electromagnetic Induction

### Classwork

- We did the first two sides of this sheet and went through the answers together.
- We went through the HW.
- We started to talk about the voltage induced across the ends of a loop or coil.
### Homework

- Complete the second two sides of the sheet linked to above. Bring to tomorrow's lesson.

## The generator effect

### Classwork

- We made some notes on the generator effect, and generating a voltage (emf) in a straight wire and in a coil.
- Here is a quick video about the generator effect though he uses a right hand rule that's different from ours, but it still gives the same result.
- We experimented with a coil and a magnet to see what factors affect the size and direction of the induced voltage.
- We started to make notes on Lenz's law.
### Homework

- Read P120-121 and add to your notes if necessary.
- Watch this video about Lenz's law and use P.123 to add to your notes.
*IMPORTANT:*in this video the guy uses a left hand grip rule - he does not mention it, but this works for ELECTRON CURRENT. We use either the right hand grip rule or the rule on P.123 for electromagnet current, because AQA always seems to deal with CONVENTIONAL CURRENT.- Answer Q1 and Q3 on P122. Bring to next lesson.

## Presentations

### Classwork

- We listened to all the presentations - well done for being organized with this.
- We started some questions about the motion of charged particles in magnetic fields.
### Homework

- Go through the notes from the talks and bring any quetions you have to next lesson.
- Finish the questions we started in class and bring to next lesson.

## Circular orbits in magnetic fields

### Classwork

- We went through the HW and added more detail to a few answers.
- We looked at the Hall effect question (Q4b) and calculated the Hall voltage, assuming that the semiconductor was 1mm wide.
- We derived the formula
r = mv/BQ for the radius of the orbit of a charged particle in a magnetic field. - We answered Q1-2 on P115.
### Homework

- Prepare a short presentation (2-3 minutes) to be given next lesson. It does not have to use powerpoint.
- NP+AM Cyclotron
- CM+NC Synchrotron
- ER+JE+NG Mass spectrometer
- PO+SM Cathode ray oscilloscope
- The first priority is to explain how magnetic fields are used (since that's what we are doing now).
- The second priority is to explain any use of electric fields, since we just learned about them.
*Note:*It would also be in your interests to do some past paper questions over the holidays - see P116-119. You should be able to do Q1, Q3, Q5, Q6a+b and Q7. Markscheme is here.- We really need to finish this chapter in the first lesson back so that we can move on to Chapter 8 ASAP.

## Charged particles in fields

### Classwork

- We made notes on the motion of charged particles in electric and magnetic fields.
- We introduced the formula
F = BQv for the force on a charged partcile in a magnetic field. - We saw a demonstration which showed a beam of electrons being deflected by electric and magnetic fields.
- I showed you this game which I made last year that lets you play around with electric and magnetic fields.
### Homework

- Answer Q1-4 on P112 and hand in tomorrow morning before registration.
- This video tries to explain the Hall effect - we will talk more about this.

## The motor effect

### Classwork

- We went through the test in detail.
- We watched a quick demo of the motor effect, discussed
F = BIl and started to discuss the DC motor. ### Homework

- Do your test corrections.
- Answer Q1-3 on P109 and hand in on Thursday morning before registration.

## Chapter 4-6 Test

### Classwork

- We did the test.
### Homework

- Recap on the motor effect and Fleming's Left Hand Rule here.
- Read and make notes on P106-7, in particular the new formula
F = BIl . We will talk more about B, the magnetic flux density, next lesson. - Watch the first two minutes of this video to remind yourself how a DC motor works (see also P108).

## Capacitor Practical Work - Continued

### Classwork

- We continued to rotate around the practical tasks, and started Part B of the past EMPA paper.
### Homework

- Revise for test next week - we will finish the Part B thing next week - bring your Part A and Part B to next lesson.

## Capacitor Practical Work

### Classwork

- We started three capacitor experiments which we will finish next lesson:
- This task is a past EMPA paper - remember all the key points about your results table and graph.
- We did a datalogging task on capacitor charging and discahrging - this is a required practical so if you missed it you have to do it next lesson.
- You built a circuit to measure the impact time of a ball bouncing on a table - we will use this next lesson to work out the impact force.
### Homework

- Revise for test next week. If you made mistakes on your HW please correct these.
- You might want to try the questions on P101 if you need more practice as the answers are in the back of the book.

## Discharging a capacitor through a resistor

### Classwork

- We did some questions on energy stored in a capacitor.
- We did a practical to investigate discharging a capacitor through a resistor.
### Homework

- Do these capacitor discharge calculations and hand in on Thursday morning.
- I will post a video to help you with this in a minute. Here it is.

## Charging with constant current

### Classwork

- We did a practical to investigate charging a capacitor with constant current.
- We looked at the graph of charge against voltage for a charging capacitor, and worked out the formula for the energy stored in a capacitor. We did this pretty quickly so we will spend more time on this.
### Homework

- Watch and make notes on this video about discharging a capacitor through a resistor.
- Read P.98-100 of the AQA textbook and add to your notes. See also P.270-271 of AP4U.
- Make sure you attempt the questions at the end of the video, and bring the answers to next lesson.

## Capacitance

### Classwork

- We investigated the relationship between the separation of capacitor plates (d) and the capacitance (C).
- We analysed our data with a graph of C against 1/d, and also with a graph of log(C) against log(d).
- We will try to do more of these log graphs in future as they are useful and can come up in the EMPA.
### Homework

- Read P94-5 and answer Q1-4 on P95. Hand in before registration on Thursday.
- You might want to watch this video about charging and discharging a capacitor with a constant current. The oscilloscope is plotting the voltage across the capacitor over time.
- The guy is using a special power supply that supplies a constant current - this is different from the power supplies that we use at school, which supply constant voltage.

## Chapter 1-5 Recap

### Classwork

- We did some recap questions on chapters 1-5.
- I did a demo of standing waves/resonance in an air column. See this video which is good.
### Homework

- Watch and make notes on this video which introduces capacitors.
- Make sure you pause and work the stuff out at the end of the video.
- Read P.94-95 of the AQA textbook and add to your notes. See also P.264-266 of AP4U.
- If you use Chrome you can see loads of satellite orbits here. Many of Disaster Monitoring look like approximately low polar orbit; they also have geostationary, the ISS and GPS satellites for you to compare orbits.

## Past paper questions

### Classwork

- We worked out how a magic floaty toy works.
- We did some past paper questions (ignore the part of 5a that is about magnetic flux density).
- Markscheme is here.
### Homework

- If you didn't do the survey in the lesson please do it tonight if you get a chance. Would be good to get your feedback.

## Catch up

### Classwork

- Since most of the people who were absent last lesson were here least lesson, we did most of the stuff from last lesson again.
- We went through the past paper questions from last week's homework using the student friendly markscheme.
- We also did some Van der Graaf demonstrations (watch this if you missed it) and explained how they worked. See
- At the end I mentioned Gauss's Law and divergence. This is not on the syllabus but it's interesting - watch this video if you are really interested in it.
### Homework

- Do some consolidation work and we will do a recap lesson on fields tomorrow, probably including some past paper questions.

## This and that

### Classwork

- We did some multiple choice questions about gravity.
- We did a variety of random problems from this page with varying degrees of success.
- We didn't do much else since there weren't many people here.
### Homework

- Do some consolidation work on fields - we need to finish fields by the end of this term so we can move on to capacitors.
- This could involve going through your notes, watching videos on YouTube, doing questions from the textbook, etc.
- Feel free to have a go at a few of these hard Oxbridge-interview-style questions.

## More Electric Fields

### Classwork

- We did some multiple choice past paper questions on fields.
- We discussed the scalar nature of potential, and the vector nature of field strength, and how this affects adding them. More on this next lesson.
### Homework

- Answer Q1-2 on P90 and bring to next lesson.

## Charge and Fields

### Classwork

- We went over the homework, and verified the results with a demonstration using a Van der Graaf generator.
- I demonstrated the shuttling ball, and we investigated the effect of varying the distance between the plates.
- We learned about the electric field strength between two parallel plates: E = V/d
- We started doing the questions on P75 and went through Q1 and Q2.
### Homework

- Read P76-79 and answer the questions on P79. Hand in on Thursday morning.
- These questions are not too hard, so please hand them in on time. Remember:
- E = F/Q and F = EQ are true in any shape of electric field.
- E = V/d is true for a uniform field between two parallel plates.
- E can be measured in Vm
^{-1}or NC^{-1}- they are equivalent.

## Introducing Electric Fields

### Classwork

- We went through the homework, and did some recap questions on gravitational fields.
- We combined the formula for centripetal force and gravitational force to find the relataionship between T and r for an object in orbit (see P66-7).
- We started to introduce electric fields.
### Homework

- Read and make notes on P72-75.
- Watch this video about electricity and add to your notes.
- Then try the examples in this video

## More Gravity Problems

### Classwork

- We went through the graphs for field strength and potential against distance from a planet, including field strength inside a planet.
- We did the questions on P65.
### Homework

- Answer Q5-7 on P70-71 and hand in any time on Wednesday.

## Potential

### Classwork

- We took some extra notes on potential, and tried to make it a more concrete concept.
- We did some calculations about potential at different heights from the earth's surface, and considered what this would mean for an object dropped from that height.
### Homework

- Complete the past paper questions and if possible hand in tomorrow morning before registration so I can mark them.
- Read P63-65 and in particular consider the graphs in Figure 2 and Figure 4 (we will discuss field strength inside planet next lesson).
- You need to be able to sketch grahs of g against r and also V against r, so look at those two graphs and think about the properties they have. I.e. if r doubles, what happens to g? What happens to V? etc.

## Gravity Problems

### Classwork

- If you missed the lesson please catch up on all this classwork before next lesson.
- We derived an expression for the gravitational field strength at a distance (r) from a point mass (m):

g = Gm/r² - This is easy and follows from F = Gm₁m₂/r² - it is also on the formula sheet.
- We did questions 2 and 4 on P55 of the textbook.
- We worked out how high above the surface of the earth you have to be for g to equal 9.5N/kg.
### Homework

- We really need to get to grips with gravitational potential as I had hoped to make a start on this today.
- Re-watch this video about gravitation potential which relates potential energy to potential and also introduces the idea of "equipotentials".
- Watch this video about gravitational potential energy. Note that U = -Gm₁m₂/r and that the zero point is at infinity, and that the gravitational potential energy is always negative.
- You can think of the gravitational potential energy of an object at a point in space as "how much energy do I need to put in to take my object from infinity to that point in space" - and since gravity is always attractive you don't ever need to put energy in to move an object from infinity towards another object - you get energy out. Hence the gravitational potential energy is negative.
- Answer Q1 and Q3 on P58 and bring to next lesson - these are very short questions.

## Newton's Law of Gravitation

### Classwork

- We introduced Newton's Law of Gravitation (see P59-61) and did all the questions on P61. There are loads of videos on YouTube - e.g. this one.
- Reminder for next lesson: look at earth-moon null point problem.
### Homework

- Try these problems.
- Watch and make notes on this video about field strength and this video about potential, and read P56-58 of the textbook.
- Next lesson we will look at field strength and potential in gravitational fields in more detail.

## Measuring g

### Classwork

- We went through the test. You all did very well.
- We recapped on the ideas of gravitational field strength and acceleration of free fall.
- We measured the acceleration of free fall by dropping balls from the balcony, and considered the uncertainty in our measurement.
- We will discuss this more next lesson as it's vital for the EMPA.
### Homework

- Watch and make notes on this video about mapping fields.
- Read pages 54-55 of the AQA textbook and page 80 of Advanced Physics for You, adding to your notes where necessary.
- Have a go at these examples.
- Do all of this before next lesson.

## Test

### Classwork

- We did the test.
### Homework

- No homeowork.

## Practice Questions

### Classwork

- We finished off the past paper questions from last lesson. (markscheme here)
- We started some hard problems with little structure - these are harder than A-Level (which would guide you through) but not impossible by any means.
- We did some BMAT questions for some reason.
### Homework

- Revise for test next Monday. You don't have to do the hard questions - do whatever you think will be useful for you.
- If you want to see them my solutions are here but I did them in a hurry so there may be mistakes.

## Finishing SHM

### Classwork

- We went through the various homework tasks set before half term.
- We looked at the applet from the homework, and also Barton's pendulums to see the phase relationship.
- We started some past paper questions from Janary 2010.
### Homework

- Revise for a test on Chatpers 1-3 next Monday.
- Here are the markschemes for the past paper questions in the textbook.

## Forced SHM

### Classwork

- We did a lengthy practical investigation into a driven pendulum. We found that maximum amplitude occurred when the pendulum was driven at the same frequency as its natural frequency (i.e. F/f was 1). This is called resonance.
- Your graph closely resembles the one on P47. The different colour curves represent different amounts of damping - the green is most damped and the blue least damped.
### Homework

- Answer Q1-2 on P49, Q5 on P52 and Q7 on P53. Hand in before registration on Thursday.
- When you have time, play around with this applet for a driven mass-spring system. Find the natural frequency by twanging the mass with the driver turned off. Then turn the driver on and see what happens. Particularly note the phase difference between the driver and the mass when:
- the driving frequency is much less than the natural frequency
- the driving frequency is equal to the natural frequency
- the driving frequency is much more than the natural frequency

- I will also post the solutions to the exam-style questions in the book in case you want to go over any extra ones over half term.

## Pendulums, springs, energy

### Classwork

- We derived the formula for the period of a horizontal mass-spring system, and noted that it works for vertical mass-spring systems too.
- We analysed the formula for the period of a pendulum but did not derive it. It's interesting to go through the derivation (see the textbook or YouTube) as it depends on the small angle approximation - so a pendulum is not really in SHM, but it's a very close approximation for small angles of swing.
- We plotted graphs of displacement, velocity, kinetic ennergy, potential energy and total energy against time.
### Homework

- Read and make notes on P44-46. I'll try to find a good video soon. How about this?
- Answer Q1-2 on P46 and hand in on Tuesday before rec.

## More SHM

### Classwork

- We went through a couple of worked examples of the use of SHM formulae.
- We investigated the relationship between the mass and the period of a mass-spring system.
- We will continue with this next lesson.
### Homework

- You really need to get to grips with the SHM formulae and their application.
- Watch this video and this video - some of this repeats what we did in class, but it doesn't hurt to see it again. If you are still unsure then try this video here too.
- Then try Q2-3 on P51 and hand these in on Thursday morning before registration.
- We do not have many more lessons to finish SHM so it's essential that you get this work done and hand it in on time.

## Simple Harmonic Motion

### Classwork

- We derived some key SHM formulae. The derivations are not required but they are very useful if you do maths or futher maths.
- I would strongly encourage you to try to solve the differential equation using your own method (i.e. not by guessing the solution as I did, since this requires practice and experience) - the differential equation to solve is d
^{2}x/dt^{2}= -kx - There are lots of ways to solve this differential equation, and if you explore the different ways (e.g. here) you will learn a lot.
### Homework

- Answer Q1-4 on P37 and hand in before registration on Tuesday.

## Oscillations

### Classwork

- We went through the homework and did an extra question on circular motion (Q7 P33)
- We looked at numerous examples of oscillations, sketched displacement-time graphs, and discussed their motion.
### Homework

- Watch this video about oscillations - the first bit is most relevant, but we will cover resonance later so you may as well watch it now.
- Read and make notes on P34-35, and make sure you are happy with all the quantites mentioned. Note that ω (from circular motion) makes another appearance here, along with phase difference (from waves at AS).
- Answer Q2-4 on P35 and bring to next lesson.

## Circular motion examples

### Classwork

- We looked at banked tracks and cars going over hills.
### Homework

- We still need to cover:
- the big dipper
- the very long swing
- the big wheel

- Read and make notes on P28-9 and answer Q1-2 on P29
- Also answer Q6 on P32
- HAND IN TUESDAY MORNING BEFORE REGISTRATION.

## Circular motion - key quantities & relationships

### Classwork

- We did some EMPA type feedback on graphs.
- We introduced the new ideas of angular displacement and angular speed, and the formulae for centripetal acceleration and force.
- This video gives a good overview of the above in the first 5 minutes or so. After that he derives the formula for centripetal acceleration which I would encourage you to watch if you are interested.
### Homework

- Watch and make notes on this video about ferris wheels.
- Answer Q1-2 on P25 and Q3-4 on P.29.
- Hand in on Thursday morning before registration.

## Circular Motion

### Classwork

- We went through the homework (markscheme here).
- We recapped on GCSE ideas about circular motion.
- We inviestivated the relationship between the centripetal force and the speed of an object in circular motion.
### Homework

- Plot a graph of your results with F on the y axis and v2 on the x axis.
- Calculate the gradient of the graph.
- The gradient is mass/radius - deduce the mass of your bung (since you know the radius).

## Even More Momentum

- We went through the homework using the student-friendly markscheme, and did some problems on water jets and springs.
### Homework

- Answer Q5-7 on P21 of AQA. Hand in before reg on Thursday.

## More Momentum

### Classwork

- We did some momentum questions, then looked at situations where an object gains or loses mass (e.g. rocket), and finally considered the change in momentum for a collision at an angle to a wall.
### Homework

- Q.2-4 on P.20 of AQA.

## Impact Force of Ball Bounce

### Classwork

- We used suvat and momentum calculations to calculate the force of a ball impact.
- You may be interested in the first graph on this page - it's about impacts of tennis balls with rackets, but it seems to show that in real collisions, impact time decreases very slightly with greater impact speed.
- Remind me to revisit ball bounce time when we do Simple Harmonic Motion, as there is a nice overlap here.
### Homework

- Watch and make notes on this video about force-time graphs. See also P.6-9 of AQA and P.52-3 of AP4U.
- Read P.14-15 of AQA and watch this video about elastic and inelastic collisions, making notes on both. See also P.66 of AP4U.

## Momentum Recap

### Classwork

- We did some recap work on momentum and introduced the concept of impulse (see P.6 of AQA and P.52 of AP4U).
### Homework

- Q.1-3 on P.13 of AQA.