EDEXCEL Unit 5 Physics Discussions - IAL only

Original post by AliNSiddiqui

Except when air resistance is forcefully added which is a core part of our learning experience, so is the resonance, which results in an increase of energy. There is a conservation in energy overall but that doesn't mean that energy can't be transformed to other forms from the system leaving the system with less energy.

Total energy is a straight line for free oscillations not forced ones..

Yes, Forced oscillation-graphs might indicate they gained energy from nothing-which is actually the impulse we apply to it.In resonance graphs we get a sudden peak, yes but thats not what i was talking about tho.

The oscillation in the question wasn't a forced one, was it? :s-smilie:

Reply 102

Original post by janine803

hi everyone, i messed up the Pb calculation....my velocity for Pb was wrong :frown:

i lost 3 marks. but can you remember the question after that? did my subsequent answers get affected by it? I don't remember any followup to that question....where we had to use the velocity of lead again, right??

I think i messed that one up too, not sure :frown:

I dont think there were any questions that depended on our earlier calculations after the momentum Q.The following ones were all qualitative i believe.

Reply 103

Original post by awesomesoccerfan

Yes, Forced oscillation-graphs might indicate they gained energy from nothing-which is actually the impulse we apply to it.In resonance graphs we get a sudden peak, yes but thats not what i was talking about tho.

The oscillation in the question wasn't a forced one, was it? :s-smilie:

i'm quite sure the question was just "SHM", didn't say what kind of oscillation.

so what's the right answer? < :frown:

Reply 104

deathbychem

Original post by Munchee

oh yes i got 1.42 J somewhere...don't remember the question tho!

hey can you please explain me how to find the change in the total kinetic energy of nitrogen molecules during the impact?
and we had to show the nitrogen molecules inside the tennis vall is about i think 5*10^21

please explain to me step by step .. :frown:

Reply 105

Original post by janine803

i'm quite sure the question was just "SHM", didn't say what kind of oscillation.

so what's the right answer? < :frown:

I think non of them, plus they always like to put tricky questions with unexpected answers lol :smile:

What did you wrote for the one about gravitational force mcq? position or weight of person?

Reply 106

Original post by Daniel Atieh

I think non of them, plus they always like to put tricky questions with unexpected answers lol :smile:

What did you wrote for the one about gravitational force mcq? position or weight of person?

what was the question exactly?? was it what will/will not affect the force on a person? what were the choices? i remeber it said mass of the person, rate of rotation of earth...what else?

Reply 107

Original post by janine803

what was the question exactly?? was it what will/will not affect the force on a person? what were the choices? i remeber it said mass of the person, rate of rotation of earth...what else?

It was about gravitational force ....
there was mass of earth and position of person

i chose position of person .. i assumed its not above the earth

Reply 108

Original post by Daniel Atieh

It was about gravitational force ....
there was mass of earth and position of person

i chose position of person .. i assumed its not above the earth

i completely forgot what the question was asking! what about gravitational force?? i picked rate of rotation for that...

Reply 109

Original post by janine803

i completely forgot what the question was asking! what about gravitational force?? i picked rate of rotation for that...

hmm kay ...
what boundary you expect for a* ? do you think this was harder than jan 14?

Reply 110

Original post by Daniel Atieh

hmm kay ...
what boundary you expect for a* ? do you think this was harder than jan 14?

I think it won't be lower than Jan 2014's 67. and i don't think it's reasonable to have a 70+, that's a little too hard no matter how "easy" a paper is.i'd say this paper is convenient, but everyone makes mistakes. so i guess 67-70. I hope 67 :P (because unit 4 was not so good for alot of us... :frown:

we need a high one for unit 5)

Reply 111

deathbychem

Original post by janine803

I think it won't be lower than Jan 2014's 67. and i don't think it's reasonable to have a 70+, that's a little too hard no matter how "easy" a paper is.i'd say this paper is convenient, but everyone makes mistakes. so i guess 67-70. I hope 67 :P (because unit 4 was not so good for alot of us... :frown:

we need a high one for unit 5)

hey we had a question about an electric heater.. right?
we had to calculate the energy
so we used E=mc delta T for that, right?
what was your ans on that?
i had something like 5.4*10^8??

and for the current i got 22.1 A?
is that what you got too?

plus how did you do the last part about the radiationnfluxx
did you use the formuale F=L/4pid^2

Reply 112

deathbychem

Original post by Daniel Atieh

I think non of them, plus they always like to put tricky questions with unexpected answers lol :smile:

What did you wrote for the one about gravitational force mcq? position or weight of person?

hey listen..
what did you write about why the gravitational field can be thought of as approximately uniform over the distance of that..i think jump?

it was a 2mark Q

Reply 113

Mouse233

3

Original post by deathbychem

hey listen..
what did you write about why the gravitational field can be thought of as approximately uniform over the distance of that..i think jump?

it was a 2mark Q

I calculated the percentage difference between 9.6smth and 9.81. The figure(1.smth%) is quite small that it can be ignored...

Reply 114

Original post by Mouse233

I calculated the percentage difference between 9.6smth and 9.81. The figure(1.smth%) is quite small that it can be ignored...

What was the answer for the 2nd mcq about which doesnt affect gravitational force? i selected position. You?

Reply 115

Original post by deathbychem

hey listen..
what did you write about why the gravitational field can be thought of as approximately uniform over the distance of that..i think jump?

it was a 2mark Q

I wrote that, compared to the circumference(2piexr) of the Earth, the length of the jumping site was insignificant so field lines are very nearly parallel.I drew a diagram of a few parallel field lines.Not sure if that's enough for the mark :frown:

Reply 116

Original post by awesomesoccerfan

I wrote that, compared to the circumference(2piexr) of the Earth, the length of the jumping site was insignificant so field lines are very nearly parallel.I drew a diagram of a few parallel field lines.Not sure if that's enough for the mark :frown:

What did you select for the second mcq? see my post up ..

Reply 117

AliNSiddiqui

2

Original post by Daniel Atieh

What did you select for the second mcq? see my post up ..

I selected Rotation rate. Changing position may cause change in height thus change in radius therefore change in gravitational field strength. And the rotation rate has no effect of the gravitational field strength as far as I am aware.. As always though, could be wrong.

(edited 9 years ago)

Reply 118

Original post by AliNSiddiqui

I selected Rotation rate. Changing position may cause change in height thus change in radius therefore change in gravitational field strength. And the rotation rate has no effect of the gravitational field strength as far as I am aware.. As always though, could be wrong.

i selected rotation rate as well. i dont know why so many picked position? in our textbooks never mentioned how rate of rotation will affect grav. force on us.....so it should be rotation rate, innit??

have to say, the MC this year was not so straight forward :frown:

so far the universe question, the SHM question and even the resonance question is debatable...

unofficial mark scheme anyone?!

Reply 119