Answers to Current of Electricity Tutorial

Please take note of the following typo in your CoE tutorial, self-attempt question 1b):

Each copper atom has 29 electrons NOT 64 electrons. (It's atomic number is 29, but mass number is 64)

S1 a) 8.98 x 10^-4 kg
b) No. of Cu atoms = 8.36 x 10^21
No. of electrons = 2.4 x 10^23
c) number of electrons moving per second = 6.25 x 10
fraction = 2.58 x 10^-5

S2) 20 C

S3 a) 600 kJ
b) 2500 C
c) 0.25 A

S4 case1: 6897 Ohm
case 2: 113 Ohm

S5 a) I = 2.0 A, R = 6.0 Ohm
b) pd = 6 V, Power dissipated = 12 W

S6 a) pd = 0.9 V, I = 4.1 x 10^-4 A
b) No change
c) R = 300 Ohm

7a) R = 0.175 Ohm
b) 3.51 x 10^-5 Ohm metre

8a) 86.4 MJ, 24 kWh
b) $3.96

9) R = 384 Ohm, l = 0.04 m

10) E = 21.1 V, r = 0.56 Ohm

11) She never give me solutions =(

12) increases by 4 times

13) We go through in class

14) 6.25 x 10^17 ions per second

15 (a)(b): E = 0.3 V, r = 1000 Ohm
(c) 0.225%

16 (b) 0.0114 Ohm
(c)(i) 1050 A
(d)(i) 1.8 x 10^5 C
(ii) 28.6 min

17(a) Total bill: $415.97

Tutorials for Term 2 Week 7

Opps I so busy with PIs that I totally forgot to blog Week 6 stuff. Heh.

Monday 4th May
Half Day (No Lessons! Woooo!)

Tuesday 5th May
IP2C: Dynamics II Tutorial Due. Finish Forces Tutorial. Start on WEP.

Wednesday 6th May
IP2C: Change of Plans. You will join Mr Yong's lab at 1030am to see a SHORT demo (on datalogger). Then you are dismissed.

Thursday 7th May
H1 Physics: Finish Dynamics I.

Friday 8th May
H1 Physics: Start Dynamics II.

Tutorials for Term 2 Week 5

Monday 20th April
IP2C: Circular Motion Tutorial

Tuesday 21st April
IP2C: Dynamics I Tutorial
Due: Circular Motion Tutorial + Assignment

Wednesday 22nd April
IP2C: PT4 (Bring long ruler for practical)

Thursday 23rd April
H1 Physics: Dynamics I Lesson

Friday 24th April
No Lessons (I am not in school - SYF rehearsal)

Tutorials for Term 2 Week 4

Monday 13 April
IP2C: Circular Motion PBI

Tuesday 14 April
IP2C: Random Stuff

Wednesday 15 April
SPEECH DAY

Thursday 16 April
H1 Physics: Linear Kinematics Topical Test. Finish Projectile Motion lesson. Start on Forces.

Friday 17 April
H1 Physics: Forces.

Tutorials for Term 2 Week 3

Monday 6th April
IP2C: Dynamics Tutorial due, Circular motion PBI

Tuesday 7th April
IP2C: Circular motion PBI

Wednesday 8th Apirl
IP2C: PT3

Thursday 9th April
H1 Physics: Projectile Kinematics

Friday 10th April
GOOD FRIDAY

Tutorials for Term 2 Week 2

Monday 30 Mar
IP2C: Due Kinematics Tutorial (SAQ, DQ and AQ). Prepare Dynamics I tutorial to go through.

Tuesday 31 Mar
IP2C: Continue with Dynamics I tutorial.

Wed 1 Apr
IP2C: April FOols Day! Circular Motion PBI (Physics by Inquiry)

Thurs 2 Apr
H1 Physics: Vectors Topical Class Test! Continue Projectile Motion lecture.

Fri 3 Apr
IP2C: Standing Broad Jump PBL due!
H1 Physics: Linear Kinematics Assignment due. Continue Projectile Motion lecture.

Tutorials for Term 2 Week 1

Monday 23 March
IP2C: We will do revision for Lecture Test, and maybe go through Dynamics Tutorial. Come with questions on any of the topics tested for Lecture Test.

Tuesday 24 March (Friday Time Table)
IP2C: Lecture Test
H1 Physics: Errors & Uncertainties Topical Class Test. Resume Kinematics lesson.

Wednesday 25 March
IP2C: Go through Practice Task 1 & 2. Please bring your SPA handout. Will finish the last part on graphs.

Thursday 26 March
H1 Physics: Resume Kinematics Lesson

Friday 27 March
H1 Physics: Projectile Motion. This lesson will be observed by HOD Science.

IP2C: Answers for Kinematics Tutorial

Below are the answers to the Kinematics tutorial. Contact me if you have difficulty arriving at the correct answers.

Rectilinear Tutorial

D1) 30 ms^-1

D2) 0.143 s

D3) Speed = 87kmh^-1 (Yes he is speeding)

D4) 10th Floor

D5) (i) -7.00 ms^-1
(ii) 0.017 s
(iii) It is correct

Projectile Tutorial

D1) 20 mm

D2) Yes it can. However, only the vertical velocity may be used for transfer to potential energy, as horizontal velocity is constant throughout the whole time of flight.

D3) (a) Horizontal = 12.1 ms^-1; Vertical = 7.0 ms^-1
(b) 0.714 s
(c) 10 cars

D4) (a) B = C, D > E, E = F
(b) A
(c) B = C, E = F, D > E
(d) A
(e) C > B, F > E
(f) F

D5) Hit the road first. Answer went through in class.

D6) (c) a = -g/(2)(u^2)(cos^2theta)
b = tan theta
c = 0

Reminder: Tutorial and Assignment due Term 2 Week 2. Dynamics Tutorial & Assignment due Term 2 Week 2 as well.

Tutorials for Term 1 Week 10

IP2C 9 Mar Monday
Due: SPA Practice Task 1
Prepare: Kinematics (both Rectilinear and Projectile) Discussion Questions and SAQ
We only have 2 lessons to discuss kinematics, and probably will not have enough time to go through every single tutorial question. I will probably focus more on projectile kinematics.

IP2C 10 Mar Tuesday
Prepare: Kinematics (both) Discussion Questions and SAQ
Last tutorial before end of Term 1. Will have one more tutorial (first day of Term 2) before Lecture Test (24th March)

IP2C 11 Mar Wednesday
SPA Practice Task 2
Please bring your SPA handout. Time permitting I will go through the remainder of the SPA handout, and your Practice Task 1 if I had completed marking by then.

H1 Physics 12 Mar Thursday
Going through Errors & Uncertainties Assignment. Start topic on Linear Kinematics.

H1 Physics 13 Mar Friday
Topical Class Test: Errors & Uncertainties
Continue lecture on Linear Kinematics

Tutorials for Term 1 Week 9

[Sorry, haven't really been updating this blog. Too busy/tired to remember. So I'll try something else instead: I'll blog during the weekend what I hope to do with tutorials for that one week. At least you all will have a heads-up this way.]

IP2C 2 Mar Monday
Prepare: Vectors (Self-attempt, discussion. Assignment if possible)
I will try to finish Vectors in one tutorial. Do your assignment if you have the time. I probably won't talk about vectors again.

IP2C 3 Mar Tuesday
Prepare: SPA handout (read everything and attempt all exercises)
I will finish the SPA handout during tutorial (so that we can start a practice task by Wednesday). If we have some extra time, may talk about Kinematics.

IP2C 4 Mar Wednesday
Due: Vectors Assignment (submit together with self-attempt and discussion questions)
Prepare: Nothing, but remember to bring long ruler for lab.
Practice Task 1.

H1 Physics 5 Mar Thursday
Topical Class Test: Physical Units & Quantities (remember to study!)
Will start on Vectors lesson

H1 Physics 6 Mar Friday
Due: Errors & Uncertainties Assignment
Continue on Vectors lesson

H1 Physics 26 Feb Tutorial

Due: Physical Quantities & Units Assignment

We'll be continuing the lesson on Uncertainties. Please bring your worked examples and study sheet.

IP2C: 23 Feb Tutorial

Due: 1) SI Units Tutorial, 2) SI Units Assignment, 3) Errors & Uncertainties Tutorial, 4) Errors & Uncertainties Assignment, in class. Hand in to me in one set.

Supposedly we were supposed to go through Vectors Tutorial, but I have decided that we spend some time on Uncertainties instead. I may not have time to go through Vectors at all, so please complete the tutorial and assignment by yourself. Will discuss with you when to hand in.

I will not go through your Pressure and Upthrust tutorial in class yet. It's actually the next topic after Kinematics (called "Forces"), so we'll go through it with the rest of the cohort. Similarly, I'll talk more about Free Body Diagrams in Term 2, which will be the topic after Forces.

But I'll post feedback and comments on your pressure & upthrust tutorial when I'm done marking it (didn't bring answer key home, so couldn't mark this weekend...=P)

For IP2C: Tutorial Stuff

Reminder: The rest of your pressure/upthrust tutorial is due tmr 19 Feb. Hand in to Yulong who will put it in my letter tray.

By now, Mr Yong would have told you that you need to do the tutorial and assignment sections of both 1)Physical Quantities & Units and 2)Errors and Uncertainties, and hand in the whole thing to me on your first tutorial next week in class. You are also expected to do the Vectors tutorial, and we are supposed to go through that the first tutorial in class.

This is a level wide thing, and I cannot make an exception for your class. In particular, since this will be recorded for purposes of your final grade (5% submitted work component), it is unfair to hold your class to separate standards. So please take note what is due the first Physics tutorial next week.

However, I very much am aware that many of you are uncertain what is going on during lecture, particularly for errors and uncertainties. I will be blogging something about it soon, so pay attention to my blog. I may also print out study sheets for you all (if I can get it done in time). At any rate, please try your best not to copy work, because when you do so, you lower your learning efficiency by around 70%. Always always try to do your own work. Wrong answers in tutorials and assignments will not be penalized for your 5% component; and you can always make appointments with me if you need more help with your tutorials or assignments.

Pressure and Upthrust Tutorial Feedback

A couple of you calculated force as pressure/area, instead of pressure x area. Very careless error, but also shows that you haven't really memorized your equation properly:

Pressure = Force / Area

Qn 1(a) Ans: 420N, 1(b) Ans: 1.5 x 10^6 N
Generally no problem with this question

Qn 2 Ans: 4400N
Some of you have a difficulty understanding the question. You need to recognize that the air inside the airplane is atmospheric pressure, i.e. 760mm mercury, while the air outside has a lower air pressure, i.e. 210mm mercury. The net force on the window is then the difference in pressure multiplied by the area. The question also wants you to use pgh to calculate pressure, instead of just using 10^6 Pa.

Q 3
I wrongly assigned this question. This is an upthrust question, will go through together with the other upthrust questions.

Q 4 Ans: 800 kgm^-3
No problem for most of you, except many of you left the answer in gcm^-3 instead of SI units. Always leave final answer in SI units unless otherwise specified.

Q 5 (a)(i) Ans: 345 kPa
(a) (ii) Ans: 245 kPa
(b) (i) Ans: 690 N

Generally not much problem for the first 3 sub-questions. Question b(ii) is very unclear what it wants from you, therefore I basically marked everybody correct. This was what the original question wanted to ask from you:

Consider the gas as an object. The force acting on the gas from the top is only 276N (are you able to get this value yourself?), but the downward force the gas is acting on the bottom of the tank is 690 N. Where does the extra 414 N of force come from?

Most of you answered something along the lines of oh Pascal's Principle states that the pressure of the tank must be the same, and hence the larger area below means a greater force is applied, since F = PA. While this statement is true, it doesn't explain where the extra 414 N comes from. So what's the real explanation?

The extra force comes from the top of the tank, the horizontal part adjacent to the shaft. What happens when you compress the gas (and hence increasing the pressure), the gas pushes outwards against the container walls. By Newton's 3rd law, all the container walls push back on the gas, exerting force on the gas. If you look at the container walls at the top of the container, the force exerted is downward, and this force accounts for the missing 414 N of force.

Second Q5 Ans: 31N
Not many people got this correct, even though the working is simple. Many identified the key concept is that the Pressure at A = Pressure at B. However, many forget to include the pgh of 8m of fluid when calculating the pressure at B.

Due Tuesday: Do the rest of the tutorial, including Q3 and the second Q5 if you have not done these questions.

Change of Location for H1 Lessons

To my H1 students, please take note that your Tuesday lessons have changed location to classroom TC15.

Monday's lessons remain in AVA room. However, AVA room is a horrible place to hold lessons, so we may hijack some unused classroom during that time slot. Will keep you updated.

This arrangement will remain until your permanent timetable is out.

Monday 16th Feb: We will be starting lesson on Physical Quantities and Units. No preparation necessary, just bring writing materials.

Tutorial for 28th July Monday

Sorry for the late update. I've been deciding what to do with this tutorial slot.

2D and 2K: We will NOT be going through the superposition tutorial. I think it is better for your new teacher to start on a fresh new unit then come into the superposition tutorial halfway. I will however, be doing a demonstration (of some sort) regarding the double slit interference experiment. So I do want you all to take a look at your superposition notes Section 1 (Principle of Superposition) and Section 4 and in particular 4.5. 2K, please be reminded that HOD science will be observing this lesson as well.

Tutorial 24th July Thursday (Monday timetable)

2K: We will not separate out the advanced learners. This is because I will not finish the unit Superposition with you, and I cannot follow through the differentiated instruction.

I need you to prepare notes for Superposition section 1, 2.1, 2.2 and 2.4 (I will upload guidelines later today). Prepare Tutorial questions 2 and 3.

2D: We will try to finish waves today. That means you should have prepared notes for sections 1.3, 4 and 3.1. And also tutorial questions 6, 7, 14, 15, and the 5 MCQ questions from the Bond and Hughes (Ch 10 Pg 11 Q1,2,3; Pg 13 Q1, 2)

2D Advanced Learners: I need you to show up for class. Some of you still owe me assignments and I also need to check if you have completed your entire tutorial as well as the compulsory questions for the Advanced Learner's Tutorial. If you have completed all that, you can come to class and do your own thing.

Tutorial for 23 July Wednesday

2P and 2K: Come with your notes for Section 4 and 3.1 Prepare the bunch of MCQ questions from your Bond and Hughes.

2K Advanced Learners: Come ready to present your findings for your enrichment task.

Tutorial for 16-17th July

16th July Wednesday

2P: I need you to prepare your own notes for Section 2, 2.1 and 2.2. If you have difficulty doing so, use this to help you. Remember to try and use your own words as much as possible! I also need you to attempt tutorial question 11 and 12. If you have any queries about what had been covered by Mr Simon Tan, or what was covered in lecture, ask me these during tutorial also.

2K: I need you to prepare your own notes for Section 1.3 (I will upload guidelines soon), and to attempt tutorial questions 6, 7, 14, 15. We stopped at question 12(d) last tutorial, and will carry on from there.

2K Advanced Learners: Your waves assignment is due. I need you to complete the compulsory questions for the Advanced Learners' Waves Tutorial, and you are free to do any of the practice questions listed. I hope to be able to go through the compulsory questions and any difficulties you faced with any of the practice questions. I will also give out your enrichment tasks at this tutorial, and you are to decide among yourselves which student to take which task.


17th July Thursday

2D: Please complete your notes for Section 2, 2.1 and 2.2 (guidelines). As well as tutorial questions 1, 2, 3, 11, 12 and 13. We will go through these questions starting from question 12. We are quite behind time because of the period I missed, so I really need all of you to do the work that I assigned to you. Come talk to me if you have difficulties. (We have already gone through question 11. If you have difficulties with that question approach me separately)

2D Advanced Learners: Your waves assignment is due. I need you to complete the compulsory questions for the Advanced Learners' Waves Tutorial, and you are free to do any of the practice questions listed. I hope to be able to go through the compulsory questions and any difficulties you faced with any of the practice questions. I will also give out your enrichment tasks at this tutorial, and you are to decide among yourselves which student to take which task.

2P: What exactly we'll do will depend on how much we cover on the 16th. I do hope that you can make your own notes for Section 1.3 by this date, and attempt questions 6, 7, 14 and 15.

Tutorials for 14 July

Monday 14th July

2K and 2D: Makes your own notes for Section 2, 2.1 and 2.2 and bring to tutorial. I will check what you have done and we will share with each other. (Refer to the below post for guidelines). Also prepare tutorial questions 1, 2, 3, 11, 12 and 13, but only AFTER you have done your notes.

2K and 2D Advanced Learners: Finish the whole waves tutorial. We will go through anything that you are uncertain about or need clarification.