Post by: Joseph41 on January 30, 2019, 03:38:39 pm
QCE PHYSICS Q&A THREAD
What is this thread for?
If you have general questions about the QCE Physics course (both Units 1&2 and 3&4) or how to improve in certain areas, this is the place to ask! 👌
Who can/will answer questions?
Everyone is welcome to contribute; even if you're unsure of yourself, providing different perspectives is incredibly valuable.
Please don't be dissuaded by the fact that you haven't finished Year 12, or didn't score as highly as others, or your advice contradicts something else you've seen on this thread, or whatever; none of this disqualifies you from helping others. And if you're worried you do have some sort of misconception, put it out there and someone else can clarify and modify your understanding!
There'll be a whole bunch of other high-scoring students with their own wealths of wisdom to share with you, so you may even get multiple answers from different people offering their insights - very cool.
To ask a question or make a post, you will first need an ATAR Notes account. You probably already have one, but if you don't, it takes about four seconds to sign up - and completely free!
Post by: K.Smithy on October 06, 2019, 12:03:23 am
I'm currently doing some work on calculating forces in 2-dimensions (when given the distance between charged particles and the charge of the particles), and there is this one worked example that I just don't understand.
I've attached photos of the question, the first photo should be the one that contains "worked example 6.1C" - I understand all of this, it is just attached for context for "worked example 6.1D". I don't understand W.E. 6.1D - what is X? Why do we need X? Why are we multiplying 90 by 1/2? How does using the first method get the same answer as using cosine rule?... I just don't get this question.
Cheers :)
Post by: K.Smithy on October 06, 2019, 12:04:26 am
Post by: DrDusk on October 06, 2019, 12:20:16 am
Here is the second image (the one with the question I am struggling with). I couldn't attach both to one post, sorry.I already don't like this textbook.. lol
Okay so basically what they've done with the whole X thing is create a right angled triangle with the angle theta in the little diagram being 90 degrees, because this would mean
This is just so that with a right angled triangle you can use your standard sin and cos stuff.
If I were you, just use the cosine rule. It's much less tedious
Post by: K.Smithy on October 06, 2019, 02:39:19 pm
I already don't like this textbook.. lol
Oml this textbook is a godsend compared to my Unit 1 & 2 textbook.
Okay so basically what they've done with the whole X thing is create a right angled triangle with the angle theta in the little diagram being 90 degrees, because this would mean
This is just so that with a right angled triangle you can use your standard sin and cos stuff.
Oh... duh... wow, I should have got that.... welp
If I were you, just use the cosine rule. It's much less tedious
Aha yeah, I much prefer cosine rule.
Thank you so much!!!
Post by: alphabeta on December 29, 2019, 10:11:09 pm
I am trying to figure out the inclined planes part of the QLD syllabus. I decided to try a QCAA question and couldn't solve it. Can someone explain how to do Q28 on paper 1 of the sample external exam for physics. I also need some great advice in general with this section, especially solving problems. Thanks!!
Post by: RuiAce on December 29, 2019, 10:40:03 pm
Hi everyone!(https://i.imgur.com/r7mkomj.jpg)
I am trying to figure out the inclined planes part of the QLD syllabus. I decided to try a QCAA question and couldn't solve it. Can someone explain how to do Q28 on paper 1 of the sample external exam for physics. I also need some great advice in general with this section, especially solving problems. Thanks!!
(https://i.imgur.com/FBvcfMQ.jpg)
There were a few steps required in this question. Let me know if there's anything you wish for me to elaborate more on.
Post by: alphabeta on December 30, 2019, 11:16:31 am
That makes sense now!. I was aware of all the steps, except didn't realise to treat the upwards applied force as friction. Thanks so much! :)
Post by: alphabeta on January 02, 2020, 11:42:36 am
I just wanted to check that I have done Q2 of the Physics practice external exam (paper 2) correctly.
So, what I have done is found the magnitude, which I got:
And for direction, I said into the page. This is the part I'm a little unsure about, as I don't quite know how much my fingers should bend. Could someone please check if what I have done is right lol?
Thanks, everyone! :)
Post by: RuiAce on January 02, 2020, 12:08:55 pm
Hi everyone! Me again.It’s definitely into the page.
I just wanted to check that I have done Q2 of the Physics practice external exam (paper 2) correctly.
So, what I have done is found the magnitude, which I got:
And for direction, I said into the page. This is the part I'm a little unsure about, as I don't quite know how much my fingers should bend. Could someone please check if what I have done is right lol?
Thanks, everyone! :)
Your thumb points in the direction of the current (which presumably you go urged yourself). Then curl up your fingers all the way. On the right of the wire, the fingers curl into the page.
(I wouldn’t actually know how the magnitude works - was never taught it. Will let someone else check your value haha)
Post by: blasonduo on January 02, 2020, 12:27:26 pm
Hi everyone! Me again.
I just wanted to check that I have done Q2 of the Physics practice external exam (paper 2) correctly.
So, what I have done is found the magnitude, which I got:
And for direction, I said into the page. This is the part I'm a little unsure about, as I don't quite know how much my fingers should bend. Could someone please check if what I have done is right lol?
Thanks, everyone! :)
Hey! By doing the question, I do get the same answer as you :) Just remember to always give units.
As Rui said, you use the right-hand grip rule :)
Post by: alphabeta on January 02, 2020, 01:57:15 pm
Quote
It’s definitely into the page.Thanks for clearing that up Rui! I wasn't sure to curl my fingers up completely, but now I know. Thanks. :)
Your thumb points in the direction of the current (which presumably you go urged yourself). Then curl up your fingers all the way. On the right of the wire, the fingers curl into the page.
(I wouldn’t actually know how the magnitude works - was never taught it. Will let someone else check your value haha)
Quote
Hey! By doing the question, I do get the same answer as you :) Just remember to always give units.Yay! Thanks blasonduo! And thanks for the reminder too, I'll remember the 'T' next time. ;)
As Rui said, you use the right-hand grip rule :)
Post by: Joshua Doland on February 01, 2020, 12:14:31 pm
Is there a QCE ATAR Notes book on Physics? I have just bought the Specialist Maths book and looking forward to receiving it in the post? Is there Physics videos for Semesters 3 & 4?
Thank you.
Joshua
Post by: K.Smithy on February 01, 2020, 02:30:35 pm
Hello my name is Joshua, this is my first time in the forum. I'm feeling my way around the website and learning how to use it and where everything is.
Is there a QCE ATAR Notes book on Physics? I have just bought the Specialist Maths book and looking forward to receiving it in the post? Is there Physics videos for Semesters 3 & 4?
Thank you.
Joshua
Hey Joshua! Welcome to the forums, I hope you enjoy your time here :)
As of currently, there aren't any subject guides for QCE Physics. Additionally, while there currently aren't any videos for QCE 3/4 physics, there is some overlap between QCE and VCE and HSC physics, so some of these videos may be helpful:
For HSC videos --> the videos on orbits and transformers may be helpful
and for VCE videos --> the videos on transformers and muons (I haven't looked too far into 3/4 physics yet. But for muons I don't think you need to know too much, I think it might just help with understanding special relativity)
Hope this helps!
Post by: A.Rose on April 28, 2020, 07:49:59 pm
I am revising Electrostatics from Unit 3 Topic 2 at the moment and I am a bit rusty! ;D I would really appreciate a little bit of help with this question, just at least to start me off :)
Question: A charged ball of mass 0.32 g hovers 2.0 cm above a charged plate that has a charge of −4.72 × 10-7 C. Calculate the magnitude of the charge on the ball.
Thank you!!
Post by: K.Smithy on April 28, 2020, 10:50:56 pm
Question: A charged ball of mass 0.32 g hovers 2.0 cm above a charged plate that has a charge of −4.72 × 10-7 C. Calculate the magnitude of the charge on the ball.
Hey A.Rose!
I'm gonna start off by saying that: I am not super confident in physics right now! It is just one of those subjects I have put on the back burner, and have been meaning to work on. So, I would take my reply with a grain of salt (just incase I have no clue what I'm talking about).
Anywho, I don't remember mass ever coming into play for questions like these, so I believe that is just an added (and unnecessary) piece of information trying to throw you off. So, I would ignore the 0.32g. If you are a bit rusty, as you said, and have no clue whether or not the mass is necessary, your go to is the formula sheet :) If you look under the "electromagnetism" section there are no formulas involving mass. So you can just rule out that bit of information.
But lets just have a look at what we think is important:
- the ball hovers 2cm above charged plate
- plate has a charge of -4.72x10-7 C
So now we can head to the formula sheet and see what we can use.
You'll see that there are two formulas that look very good:
F = 1/4πɛ0 x Qq/r2 AND E = 1/4πɛ0 x q/r2
(keeping in mind that 1/4πɛ0 = k = 9x109 - also be careful with units, I'm fairly certain that the distance should be in meters so just make sure you do any necessary conversions)
Because we aren't looking for the force we can rule out the first formula - leaving us with the second one.
Therefore, I would start off by using: E = 1/4πɛ0 x q/r2
(Once again, I could be entirely wrong. But this is what I would do anyway... I hope I'm not wrong tho and I hope this helps ;D - good luck!)
Post by: Bri MT on April 29, 2020, 03:04:39 pm
Hello!
I am revising Electrostatics from Unit 3 Topic 2 at the moment and I am a bit rusty! ;D I would really appreciate a little bit of help with this question, just at least to start me off :)
Question: A charged ball of mass 0.32 g hovers 2.0 cm above a charged plate that has a charge of −4.72 × 10-7 C. Calculate the magnitude of the charge on the ball.
Thank you!!
K. Smithy you weren't quite there but you were on the right track.
The trick to this question is recognising that since the ball is hovering, it is stationary with 0 net force. Thus, force due to gravity and force to the electric field strength cancel out.
If we take the magnitude of those two forces as being equal:
\[ mg = \frac{1}{4 \pi \varepsilon_0} \frac{qQ}{r^2} \]
all you need to do is sub in values appropriately (as K.Smithy said, be careful with units) and solve for q
Edit: for showing fractions neatly in latex it's \frac{}{} . I didn't learn it for a while on the forums but there's a great guide by Rui here
Post by: K.Smithy on April 29, 2020, 07:31:08 pm
K. Smithy you weren't quite there but you were on the right track.
Aha worth a shot! ;D Hopefully i'll get there before the externals :)
Thanks for clearing it up!
Post by: Bri MT on April 29, 2020, 07:48:26 pm
Aha worth a shot! ;D Hopefully i'll get there before the externals :)
Thanks for clearing it up!
No worries!
I'm sure you will :)
Post by: A.Rose on April 29, 2020, 08:01:18 pm
The trick to this question is recognising that since the ball is hovering, it is stationary with 0 net force. Thus, force due to gravity and force to the electric field strength cancel out.
Thank you both for your help! Yes, I did work out that I needed the mass to calculate the force eventually. :)
I definitely need to do some thorough electrostatics revision! :D
Thanks!!
Post by: Bri MT on April 29, 2020, 08:14:18 pm
Thank you both for your help! Yes, I did work out that I needed the mass to calculate the force eventually. :)
I definitely need to do some thorough electrostatics revision! :D
Thanks!!
No worries!
This stuff is pretty standard across states so if you want more revision you should be able to find a bunch from other states.
Post by: A.Rose on April 30, 2020, 12:56:38 pm
I am very confused about this question. (The diagram is attached). The question is to 'explain using physics concepts how the system will operate to close and open the tubing'.
A student designs a simple solenoid valve system to control the flow of a liquid through flexible tubing by closing and opening the tubing. It is comprised of an iron rod with a spring coiled around it at one end. One end of the spring is attached at one end of the rod and its other end is attached to a rectangular housing. The tubing is fixed to a solid support.
If you could at least direct me to where I can find a good explanation of how these kinds of experiments work because I don't remember learning about solenoids in this kind of context last year. I'm assuming its something to do with the establishment of a magnetic field that opens or closes the tube - but I am not confident. Just some clue or somewhere I can research this (I didn't have much luck in my textbook or searching online) that would be amazing!!
Thank you!
Post by: Bri MT on April 30, 2020, 02:03:12 pm
Hi! Me again with another question! ;D
I am very confused about this question. (The diagram is attached). The question is to 'explain using physics concepts how the system will operate to close and open the tubing'.
A student designs a simple solenoid valve system to control the flow of a liquid through flexible tubing by closing and opening the tubing. It is comprised of an iron rod with a spring coiled around it at one end. One end of the spring is attached at one end of the rod and its other end is attached to a rectangular housing. The tubing is fixed to a solid support.
If you could at least direct me to where I can find a good explanation of how these kinds of experiments work because I don't remember learning about solenoids in this kind of context last year. I'm assuming its something to do with the establishment of a magnetic field that opens or closes the tube - but I am not confident. Just some clue or somewhere I can research this (I didn't have much luck in my textbook or searching online) that would be amazing!!
Thank you!
Hey!
You're on the right track! Current carrying solenoids create magnetic fields like the field around bar magnets.
This exact question type isn't common but there are often questions involving magnetic fields around solenoids in VCE physics so it might be worth looking at some of those.
I'm aware I've been pretty vague here (you seemed to be on the right track) - please feel free to follow up with anything you're unsure of :)
Post by: elmobluey on May 02, 2020, 10:33:41 pm
I'm confused on the working that my teacher has provided on a recent practise data test we did.
I have attached the dataset and the question. I really don't have a clue on what my teacher has done. I thought I would have seen "9.81m/s/s" somewhere in the working. But... Yeah I really have no idea what's going on here. Can anyone explain to me why the acceleration due to gravity is 12.5m/s/s?
Thank you!
Post by: Bri MT on May 03, 2020, 09:57:24 am
Hi!
I'm confused on the working that my teacher has provided on a recent practise data test we did.
I have attached the dataset and the question. I really don't have a clue on what my teacher has done. I thought I would have seen "9.81m/s/s" somewhere in the working. But... Yeah I really have no idea what's going on here. Can anyone explain to me why the acceleration due to gravity is 12.5m/s/s?
Thank you!
Hey!
This is a question saying if the data we had was x, then what would that mean about y? Sometimes this will end in a reasonable value and sometimes it won't. The reason you don't see the actual value for g is because the question wants you to pretend you don't know what this is & figure out what it would be for the provided fake situation.
Do you understand where g = sin(theta) comes from?
Post by: A.Rose on May 05, 2020, 03:22:41 pm
I just need a clue to where to start. Since its asking for speed I'm assuming I'm going to need to use F=qvB at some stage...? But it also gives me a potential difference which makes me think I need to use ∆U=∆Vq? Am I at least on the right track or is there something I'm missing?
Thank you!
Post by: Bri MT on May 19, 2020, 01:51:29 pm
Hi, I have another Electromagnetism question! Please see attached.
I just need a clue to where to start. Since its asking for speed I'm assuming I'm going to need to use F=qvB at some stage...? But it also gives me a potential difference which makes me think I need to use ∆U=∆Vq? Am I at least on the right track or is there something I'm missing?
Thank you!
Sorry I somehow missed this earlier!
You may have resolved this by now, but my approach would be to use the change in energy to get the kinetic energy and thus speed :)
Post by: chantal.duffy on July 08, 2020, 11:00:59 am
Thank you! Hope everyone is keeping well.
Post by: chemistrykind on July 08, 2020, 11:06:56 am
Hi everyone! If someone could help me out, I would really appreciate it. I've attached a photo of some diagrams regarding F=qvBsinθ. Can someone just confirm for me what the answers are for each of these? The Textbook doesn't have any answers and I've been finding these pretty difficult so I just want to confirm that I've been getting it right. It uses Fleming's Left-Hand Rule.
Thank you! Hope everyone is keeping well.
Looks like left, up, out of the page, into the page! Hope ur studies are going well :0
Post by: chantal.duffy on July 08, 2020, 11:28:32 am
Looks like left, up, out of the page, into the page! Hope ur studies are going well :0
Absolute legend!! Thank you very much :)
Post by: A.Rose on August 04, 2020, 03:00:02 pm
I just need some help with this question - a little confused with what is happening...what is the stopping length?
Thank you!
Post by: Bri MT on August 04, 2020, 03:03:42 pm
It's asking you how much distance the truck will cover before coming to a stop.
Post by: A.Rose on August 04, 2020, 03:12:27 pm
Post by: Bri MT on August 04, 2020, 03:21:45 pm
Oh ok, so its how much distance the truck will cover on the ramp before stopping...? Just need another clue. I'm not given its mass or anything just initial velocity and an angle. Usually, inclined plane Q's I need the parallel component...?
Yeah it's how much distance the truck would cover on the ramp before stopping.
This isn't a standard inclined planes question, it's about using the constant acceleration formulas (keeping in mind that unlike weight which would need you to know mass, acceleration due to gravity is constant on the surface of Earth - combine this with knowing the angle).
You've been given initial velocity & you set final velocity equal to 0 (because its stopping distance)
Post by: A.Rose on August 04, 2020, 04:21:54 pm
Post by: schoolstudent115 on August 04, 2020, 04:41:06 pm
HelloYou can also use energy to solve this (I prefer this method).
I just need some help with this question - a little confused with what is happening...what is the stopping length?
Thank you!
Initial KE: 1/2 * m * (16.7)^2.
Work done by ramp = L*mg*sin(15), L is the length (this is just W = Fs)
Then equate the two, the masses will cancel out.
Post by: matthew hay on August 26, 2020, 06:41:41 pm
Do you or anyone know if there is an annotated syllabus? or even annotated Units 4 syllabus?? Please reply no if not (it saves me the extravagant search!
Thanks and kind regards, Matt
Post by: Bri MT on August 26, 2020, 07:45:08 pm
I don't know of any physics syllabus annotations but if this is something you're really interested please feel free to let me know!
Post by: matthew hay on August 29, 2020, 06:56:17 pm
Yes, an annotated syllabus would very helpful and useful !!! :D
Post by: jasmine24 on November 05, 2020, 07:15:33 am
Thank u!
Post by: Bri MT on November 06, 2020, 11:18:57 am
Hi, would anybody have any examples on "interpreting graphical representations of electrical potential difference vs electric current data to find resistance using its gradient and its uncertainty". I couldn't find any that also found the uncertainty and I'm unsure as to how to do that
Thank u!
Hey,
I'll attach some images later today but remember that this just comes from Ohm's law V=IR => V/I = rise/run = gradient = R
In regards to uncertainty, what's the steepest line of best fit given your uncertainty? What's the least steep line of best fit? Constructing these will give you your range of values for R and hence your uncertainty.
Hope this helps!
Post by: K.Smithy on November 06, 2020, 06:25:13 pm
I have been talking to a few people about this question and we haven't been able to come to an agreed upon answer :P
(https://i.imgur.com/Pe6DeXc.jpg)
For part a, some think that the charge of Q2 is negative and Q1 is positive: due to the fact that they opposite charges the electric field strength would cancel out in the middle. Furthermore, the electric field strength is negative as you approach Q2 - therefore, Q2 has a negative charge.
Others think that both Q1 and Q2 are positive: Coulomb's law states that opposite charges attract and like charges repel - so that would explain the fact that the electric field strength is 0 in between the two point charges (if both are positive, they will repel each other).
I can see both sides, but I don't know which one is correct.
Thanks,
Katelyn :)
Post by: Bri MT on November 08, 2020, 01:28:08 pm
Q2 is positive, because of the zero as well as because it goes from positive to negative. Electric field strength is described in terms of the impact of a positive charge at that point in space, not in terms of how the two charges present would interact so the second pov doesn't really work despite it showing physics knowledge.
Good question - it's an interesting one that I can easily see being one people would argue about after an exam
Post by: K.Smithy on November 08, 2020, 01:34:13 pm
Hi K.Smithy! :)
Q2 is positive, because of the zero as well as because it goes from positive to negative. Electric field strength is described in terms of the impact of a positive charge at that point in space, not in terms of how the two charges present would interact so the second pov doesn't really work despite it showing physics knowledge.
Good question - it's an interesting one that I can easily see being one people would argue about after an exam
Awesome! Thank you so much :)
Post by: Bri MT on November 08, 2020, 04:18:53 pm
Awesome! Thank you so much :)
No worries!
For questions like this I would really recommend drawing a field diagram to help you understand why the answer is what it is. Once you've drawn it you should be able to see that for positive -> negative the field is constantly from q1 to q2 but that for positive -> positive it isn't since both positives are trying to push positive charges away & therefore are acting in opposite directions.
Post by: jasmine24 on November 09, 2020, 07:51:07 am
Thank you
Post by: Bri MT on November 09, 2020, 10:53:51 am
hi, i was wondering how Lenz's law is consistent with the principle of conversation of energy
Thank you
Hi,
Hopefully this reaches you before paper 2!
I encourage you to draw out how you could get a situation with infinite electrical energy if Lenz's law wasn't true by having positive feedback loop of: more current -> more change in flux -> more current -> more change in flux etc.
Another way to think about it is to take the situation of moving a coil towards a bar magnet. As the coil moves the change in flux will induce current in the coil and thus the coil will generate a magnetic field. This magnetic field will have a north and south end and consequently there will be attraction or repulsion between the coil and bar magnet. This attractive or repulsive force will act over the displacement of the coil (W=Fx) and this work balances the change in electrical energy.
I've included a rough diagram below where you can see that as the distance between the bar magnet and loop decreases the generated magnetic field is such as to generate repelling force.
(https://i.imgur.com/AqHP2s9.png)
Post by: jasmine24 on May 18, 2021, 04:45:18 pm
Post by: fun_jirachi on May 18, 2021, 04:56:53 pm
Consider fixing random error at ±0.1s. A longer plane may take 3s + random error, while a smaller plane may take 2s + random error. This is an unrealistic example but hopefully, this demonstrates that longer inclines will minimise the impact of random error on your experiment (thus providing more consistent results). It's the same reason why we choose compounds of high molar mass for standard solutions in chemistry.
Hope this helps :)
Post by: jasmine24 on May 23, 2021, 08:57:38 pm
TIA
Post by: K.Smithy on May 23, 2021, 09:31:12 pm
what is the relationship between the length of an inclined plane and acceleration? All ik is that as displacement increases, acceleration decreases but I'm not sure why
TIA
As you increase the length of a ramp, you decrease the angle that the ramp has to make with the ground.
A greater angle will result in greater acceleration. Thus, a shorter ramp/shorter displacement will result in increased acceleration. Whereas, a longer ramp will result in decreased acceleration.
I have drawn a little picture to help us think about this (prepare yourself for what is sure to be the best drawing you've ever seen in your entire life - no cap):
(https://i.imgur.com/DhRYHUZ.png)
As you can see on the image above, we have two people who are about to roll down a hill. In condition 1, the ramp is longer - meaning the angle is smaller. In condition 2, the ramp is shorter - meaning the angle is larger.
Who do you think will roll down the hill faster? The person in condition two, right? Yes. Honestly, that hill looks like it would hurt to roll down lol.
Hope this makes sense :)
Post by: justsomerandom21 on July 13, 2021, 05:33:58 pm
Post by: K.Smithy on July 18, 2021, 06:04:38 pm
Hi does anyone recommend memorising all the notes we're given in class by our teachers or just the syllabus dot points?
I had my fair share of teachers who covered content that wasn't super important. I would recommend putting all of the syllabus dot points onto a word document and filling your notes underneath each dot point so that you know you've covered it all. At least for the theory-based dot points. For the practical-based calculation type dot points, just do practice questions. I noticed you asked the same question for biology, I recommend this method for that as well. It ensures that you have everything you need.
Post by: justsomerandom21 on July 18, 2021, 08:06:34 pm
I had my fair share of teachers who covered content that wasn't super important. I would recommend putting all of the syllabus dot points onto a word document and filling your notes underneath each dot point so that you know you've covered it all. At least for the theory-based dot points. For the practical-based calculation type dot points, just do practice questions. I noticed you asked the same question for biology, I recommend this method for that as well. It ensures that you have everything you need.Thanks so much for the advice!! I've had a bit of a hectic year with so many of my teachers leaving my school and me just trying to survive the school year...I really appreciate this!
Post by: jasmine24 on August 03, 2021, 10:29:35 am
thanks!
Post by: Billuminati on August 03, 2021, 11:24:38 am
just a quick question, if a study I'm using may be slightly outdated, does it affect its reliability or validity?
thanks!
If the source you’re trying to reference is designed well and controls all variables except for the independent variable, then it’s valid. If its result data points are pretty consistent with each other, then it’s also reliable. However given its age, there may be new advances in the field such that the values reported may not necessarily be accurate anymore ie close to the true values that we know of now
Post by: jinx_58 on August 18, 2021, 08:32:07 pm
What would be a good example of Newton's first, second and third laws?
Thanks,
- jinx_58
Post by: K.Smithy on August 18, 2021, 08:58:56 pm
Hey everyone.
What would be a good example of Newton's first, second and third laws?
Thanks,
- jinx_58
Hey Jinx_58,
1st Law Example: the experience of being "thrown" forward when your car comes to an abrupt stop. Why is this an example of Newton's first law? Well, the first law is known as the law of inertia (where inertia is the tendency of a body to resist a change in velocity). You'll often hear: "A body in motion remains in motion, and a body that is stationary remains stationary, unless acted upon by an unbalanced external force." So, with the example of being thrown forward when your car comes to a stop... Your body's inertia wants to keep you moving forward, however the car (acting as an unbalanced external force) stops you from being able to continue on this path.
2nd Law Example: If you have 2 boxes (one of mass 10kg and one of mass 100kg) and you want to push them both forward with an acceleration of 0.5ms-2, you will require much more force to push the 100kg box at that speed, than you would the 10kg box.
3rd Law Example: If you throw a tennis ball at the ground it will bounce back up into the air. Why? Because newton's third law of motion states that every action has an equal and opposite reaction. When you throw the ball at the ground, it exerts a force on the ground. The ground also exerts the same magnitude of force back on the ball - only it acts upwards. Thus, the ball is propelled upwards.
Hope this helps
Post by: jinx_58 on August 18, 2021, 09:45:18 pm
Post by: jinx_58 on September 05, 2021, 08:53:03 pm
I'm having trouble meeting the following Unit 1 success criteria:
1. explain that a system with thermal energy has the capacity to do mechanical work
2. explain natural radioactive decay in terms of stability
3. describe energy in terms of electron volts (eV) and joules (J)
I'm having trouble meeting the following Unit 2 success criteria:
1. explain the formation of standing waves in terms of superposition with reference to constructive and destructive interference, and nodes and antinodes.
2. construct free-body diagrams representing forces acting on an object
3. describe polarisation using a transverse wave model
4. contrast the speed of light and the speed of mechanical waves
Any help would be appreciated.
Regards,
jinx_58
Post by: jinx_58 on September 18, 2021, 03:58:23 pm
I was looking through Unit 2 content and found this problem:
A child seating in a rowing boat initially at rest throws a package of mass 5kg out of the back with a speed of 10m/s. Determine the speed and direction of the boat immediately after the package was released if the child weighs 24kg and the boat weighs 40kg.
I have attached the working I've done so far.
Could someone please help?
- jinx_58
Post by: noor.fatimaaa on September 19, 2021, 03:49:45 pm
Does an anyone know what I can write in my rationale
I am working on a physics IA2 and the experiemtn is on the angle of a ramp and the displaceemnts affect on time
My teacher has told me to research about a theory and put it in my rationale. Which theory can i use? What else can i write about in my rationale?
Please help
Post by: Gracey1415 on October 09, 2021, 11:51:33 am
I have no idea how to figure out the distance x here, any help would be appreciated :)
I have attached the question and the answer is supposed to be 1m but idk how
Post by: K.Smithy on October 09, 2021, 12:11:42 pm
question reguarding distance between an electric field and charges.
I have no idea how to figure out the distance x here, any help would be appreciated :)
I have attached the question and the answer is supposed to be 1m but idk how
Hey Gracey1415!
If you get a question like this where you are finding the electric field strength at a given point due to multiple sources, then you will need to do a superposition of the electric field (essentially combining the electric fields produced by either source).
In this case, you are able to do a simultaneous equation implementing the expressions for the electric fields resulting from each point charge - then you can just solve for x.
Here is the working I did to get the answer
(https://i.imgur.com/VsHHRZ2.png)
Apologies for my terrible trackpad writing ahaha.
I hope this working out makes sense, but feel free to give us a shout if you are still having some trouble with it and I'd be more than happy to help out a bit more :)
Katelyn
Post by: Gracey1415 on October 09, 2021, 01:05:51 pm
Hey Gracey1415!
If you get a question like this where you are finding the electric field strength at a given point due to multiple sources, then you will need to do a superposition of the electric field (essentially combining the electric fields produced by either source).
In this case, you are able to do a simultaneous equation implementing the expressions for the electric fields resulting from each point charge - then you can just solve for x.
Here is the working I did to get the answer
(https://i.imgur.com/VsHHRZ2.png)
Apologies for my terrible trackpad writing ahaha.
I hope this working out makes sense, but feel free to give us a shout if you are still having some trouble with it and I'd be more than happy to help out a bit more :)
Katelyn
Thanks so much!
Why should you disregard the negative for the 18 coulombs?
Post by: K.Smithy on October 09, 2021, 01:23:56 pm
Thanks so much!
Why should you disregard the negative for the 18 coulombs?
When you use formulae such as this one and Coulomb's law, you're interested in the magnitude of the electric field strength or the magnitude of the force. So, if you had a Coulomb's law question and you had one point charge of 2 µC separated from a second point charge of -2 µC by a distance of 2 m, then you would disregard the negative in your calculations for the magnitude of the force.
So you would have
F = ((9*109)(2*10-6)(2*10-6))/22
Rather than having a negative 2 for one of the Qs
F = ((9*109)(2*10-6)(-2*10-6))/22
This is because we are simply interested in the magnitude of the force (which will always be presented as a positive number). The signs of the charges will tell us whether the force between the charges will be attractive or repulsive. In this case, we know that the force between them will be attractive. This is because Coulomb's law tells us the opposite charges attract.
Similarly, when we are working with electric field strength we are interested in the magnitude. So we can leave the negative off of the -18µC charge. All it tells us is that the electric field from the negative point charge will oppose that of the positive 2µC point charge. Meaning they will cancel out. If you put the negative in the calculation, then when you do your simultaneous equation the will add together (instead of cancel out) and you will get the wrong answer for distance.
I hope this makes a little more sense :)