Forumers, ask your Physics questions here ! (compilation)
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Originally posted by senga:
New guy here. I have a question for Eagle. So yesterday I ask ultimaonline how I should go about studying for a levels chem. He recommend I get CS Toh study guide and start doing yearly TYS. Should I use this approach for chemistry and math??
I recommend you Eagle's(Tan Jun Wei's) H2 physics book, available at Popular, Cstoh's math and physics book, available through their website and through their carousell account.
i would also recommend you to do yearly TYS , revise, mark, do corrections on your own.
can wait for expert Eagle's advice too, when he replies.
if needed, can consider joining Ultimaonline's and Eagle's high quality tuition.
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Originally posted by eagle:
Hi iSean,
the procedure you have listed is already extremely clear. How much clearer do you need?
In my opinion, you are lacking certain Physics concepts to be unable to understand the procedures.
I notice that you did not specify the level of the question.
Are you an O level student?
Or if you are an A Level student, did you take Pure Physics during O Level, or just combined science?Your physics concepts that seems to be lacking from O Level are
1) Work Energy Power
2) Thermal Properties of Matter
3) Circuits as well as Practical Electricity
and the combination of these topics together.You have too many concepts missing, and no indication of which level of study you are at, so I have no idea where to start advising you too. :x
I think I'd contacted you before regarding purchasing your H2 Physics Book and SPA Planning book for an e-Book version to be purchased overseas, not mistaken you are Mr Tan Jun Wei right?
So, I study in Malaysia, now doing CIE A2 of A-Level in a Private College, like all Malaysians doing CIE A-Levels here, if they don't plan to join Government STPM.
(STPM is not favoured by students here because it is hell compared to A-Levels.)
But my main problem is my understanding is mostly towards O Level (SPM), because of I don't think I really grasp my O Level Foundation well, despite getting an A- for my SPM. With the fact, I sleep through secondary school Physics Classes, and eventually attended tuition classes after school. Getting an A- for SPM Physics was a miracle, by memorizing formulas and substitute them, and my most hated Chapters was Light in my 4th Form.Also my problems worsen here, as my Private College is also an issue whereby, despite paying RM 23K for tuition fees. The colleges always tends hire newly fresh graduated lecturers with no teaching experience. Eventhough, I got a Physics PhD Holder to teach my class. It seems like he doesn't really knows how to teach to students. I will always forget everything after his lectures, despite doing exercises.
Eventually, I basically self-studied all the way throughout AS Levels and reading multiple coursebooks, and referencing Longman's H2 Physics, Youtube, KhanAcademy and Google, to learn all at my own pace.
(I didn't seek a tutor outside anymore, because RM 23K is bloody expensive tuition fees)
All and all, I'm basically one messed up A-Level students, with 4 unstable subjects now doing A2. -
Originally posted by eagle:
Hi iSean,
the procedure you have listed is already extremely clear. How much clearer do you need
Erm basically I don't understand why the experiment is determined like so at first,
I was thinking, regarding when I need to start timing, and when I need to collect the water. As my lecturer told me the timing and water collected, will be when you just start the experiment, as the temperature is not constant yet.
But eventually I think I now get the concept after consulting with another friend from another class.
Regarding the experiment,
I need to first continously flow water through the tube, and I won't need to collect any water until input and output temperature as the same.
Then measure the first set of voltage and current. And start my timer for fixed interval of 5 minutes to collect my mass of water.
Then, I turn up my variable rheostat to a higher voltage(higher resistance) and increase the flow rate, and I will not to collect any water until the temperature of input and output temperature are constant.
But if my temperature change is too high or too low, which is not the same as the first set of data, I need to readjust until the rheostat it has the same temperature change as the first data set.
And start my timer for 5 minutes to collect the water again.
But I'm still quite curious regarding now, how will collect the water.
Also, should my input temperature will be the same, assuming that the heat coil won't transfer heat to the input thermometer, as water is always flowing away from the input thermometer?
(English isn't my first language, sorry for being too long winded.) -
Hi iSean,
*Before we continue, do take note that Cambridge A level will not explicitly test you on this experiment on how you should approach doing it, although you should know it. To do well, you need to focus on the things that they test more frequently on.*
The input and output temperatures are always adjusted to be the same to ensure that any heat loss to surroundings is kept constant. As such, we are able to let it be a constant which can be deducted.
The formula involved is Pt = mc Δθ + H, where H refers to the heat loss to surroundings.
Let's go into the details of the experiment.
Δθ and t are variables to be kept constant so that H becomes constant, because rate of H depends on the temperature difference between the water and the surroundings.
c is a constant which you need to measure.
m is the mass of the amount of water collected.
For the experiment, you need to vary P by whatever means you have learned in Circuits (i.e. varying resistances, current, p.d., or even e.m.f.), and adjusting the flow rate to ensure Δθ and t are constant to ensure a constant H.
Because the flow rate is varied, different values of P will give different values of m, the mass of water collected.
So by doing the experiment with two different values of P, you will get
P1 t = m1 c Δθ + H -------- (1)
P2 t = m2 c Δθ + H -------- (2)Because you have kept Δθ and t constant, H will be a constant. Hence, we are able to take (2) minus (1) and eliminate H.
From there, the value of c can be determined because every other variable is known (maths concept of simultaneous equations).
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Originally posted by eagle:
Hi iSean,
*Before we continue, do take note that Cambridge A level will not explicitly test you on this experiment on how you should approach doing it, although you should know it. To do well, you need to focus on the things that they test more frequently on.*
The input and output temperatures are always adjusted to be the same to ensure that any heat loss to surroundings is kept constant. As such, we are able to let it be a constant which can be deducted.
The formula involved is Pt = mc Δθ + H, where H refers to the heat loss to surroundings.
Let's go into the details of the experiment.
Δθ and t are variables to be kept constant so that H becomes constant, because rate of H depends on the temperature difference between the water and the surroundings.
c is a constant which you need to measure.
m is the mass of the amount of water collected.
For the experiment, you need to vary P by whatever means you have learned in Circuits (i.e. varying resistances, current, p.d., or even e.m.f.), and adjusting the flow rate to ensure Δθ and t are constant to ensure a constant H.
Because the flow rate is varied, different values of P will give different values of m, the mass of water collected.
So by doing the experiment with two different values of P, you will get
P1 t = m1 c Δθ + H -------- (1)
P2 t = m2 c Δθ + H -------- (2)Because you have kept Δθ and t constant, H will be a constant. Hence, we are able to take (2) minus (1) and eliminate H.
From there, the value of c can be determined because every other variable is known (maths concept of simultaneous equations).
I just like to analyse the procedure on how to do the experiment itself, to get the bigger picture. :)
Well i think I finally understand the full story now. Thanks Eagle. -
May I ask, why the answer is not B/C/D? But A instead?
I thought Centripetal force always act towards to the centre of the curviture ?
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Centripetal force is a resultant force and is not to be drawn into a free body diagram. This is because it is a resultant of all forces acting on the object.
It is a resultant because it gives rise to an acceleration.
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Eagle, do you mind uploading one or two pages of your physics book? it's mostly on planning qns and qualitative questions right?
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Originally posted by eagle:
Centripetal force is a resultant force and is not to be drawn into a free body diagram. This is because it is a resultant of all forces acting on the object.
It is a resultant because it gives rise to an acceleration.
Hmmmm I see.
So, I assume it always tries to acts towards the centre of curviture then?
Means that my reference point 'x' is a cone pointing upwards? -
iSean, centripetal force always acts towards the centre of the circular path, not vertex of a cone. It is always perpendicular to the direction of motion.
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Originally posted by Flying grenade:
Eagle, do you mind uploading one or two pages of your physics book? it's mostly on planning qns and qualitative questions right?
mostly qualitative. I don't have a softcopy at the moment as I outsourced it to a friend to do.
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Hi i need some help...
Which of the following will not reduce random errors in your experimental measurements?
a) double the weight of magnesium used to a calorimetry experiment
b) use a thermometer with a smaller scale
c) use activated and finer magnesium granules
d) use a larger calorimeter with the same volume of solution
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Originally posted by Nikkilyx:
Hi i need some help...
Which of the following will not reduce random errors in your experimental measurements?
a) double the weight of magnesium used to a calorimetry experiment
b) use a thermometer with a smaller scale
c) use activated and finer magnesium granules
d) use a larger calorimeter with the same volume of solution
d.
for a) , deltaT will increase, lessening random error
b) that reduces the chance of parallax error, a systematic error. but it also reduces random error as more scale divisions results in more precise readings by the eye
c) reduces sporadic reactions, ensure more even reaction hence more consistent heat production
d) not sure what positive or negative effect of using a larger calorimeter would be. maybe more contact with walls of calorimetry . less heat released to the water