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Author Topic: Edexcel PHYSICS Doubts  (Read 121381 times)

Offline Nobody

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Re: Edexcel PHYSICS Doubts
« Reply #705 on: June 06, 2011, 12:07:32 am »
Problem solved. :)
so, you're marring him now? ::) :P

reaction time is normally used only when you have to time something.
like calculating the time for a pendulum to complete 10 oscillation.
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Offline Assi1993

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Re: Edexcel PHYSICS Doubts
« Reply #706 on: June 06, 2011, 12:14:08 am »
Quote from: Romeesa-Chan on June 06, 2011, 12:05:09 am
Please don't temme my graph is wrong! :P

well u should have used a different scale..with shorter intervals..like 6.4,6.6,6.8

and...go through the examiner reports..they have explained about how to do the line of best fit etc
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Offline Dangerous99

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Re: Edexcel PHYSICS Doubts
« Reply #707 on: June 06, 2011, 12:15:05 am »
lol im only 18  :P
Thanks for ur help By the way, i mustve been eating ur head tonite :-[
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Offline Romeesa-Chan

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Re: Edexcel PHYSICS Doubts
« Reply #708 on: June 06, 2011, 12:16:45 am »
Quote from: Assi1993 on June 06, 2011, 12:14:08 am
well u should have used a different scale..with shorter intervals..like 6.4,6.6,6.8

and...go through the examiner reports..they have explained about how to do the line of best fit etc

Sure! ;)

Thanks! :D
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Offline Nobody

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Re: Edexcel PHYSICS Doubts
« Reply #709 on: June 06, 2011, 12:21:15 am »
Quote from: Romeesa-Chan on June 06, 2011, 12:05:09 am
Please don't temme my graph is wrong! :P

the graph is good.
Quote from: Assi1993 on June 05, 2011, 11:51:01 pm

In this, u can take the coordinates(0,6.869) and (31.74, 5.257)



the graph goes a BIT away. makes sure you don't repeat it. ;)
and, like Assi1993 said use a shorter scale. ;)


Quote from: Dangerous99 on June 06, 2011, 12:15:05 am
lol im only 18  :P
Thanks for ur help by the way, i mustve been eating ur head tonite :-[

you said so. didn't you? ;) :P
nah, that's what we're here for.
Helping you guys. :)
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Offline Romeesa-Chan

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Re: Edexcel PHYSICS Doubts
« Reply #710 on: June 06, 2011, 12:29:20 am »
Quote from: Assi1993 on June 06, 2011, 12:14:08 am
well u should have used a different scale..with shorter intervals..like 6.4,6.6,6.8

and...go through the examiner reports..they have explained about how to do the line of best fit etc

By the way, what if we get negative value for the gradient? We don't put the -ve sign, right?
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Offline Romeesa-Chan

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Re: Edexcel PHYSICS Doubts
« Reply #711 on: June 06, 2011, 12:32:25 am »
Never mind. I got it! :D
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Offline studz

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Re: Edexcel PHYSICS Doubts
« Reply #712 on: June 06, 2011, 05:30:10 am »
thanks a lot nobody for the uncertainity part
though it is still kinda confusing but anyway hope all goes well today!
good luck to all  :D

and lmao at the marrying part hehe!!  :P
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Offline Nobody

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Re: Edexcel PHYSICS Doubts
« Reply #713 on: June 06, 2011, 04:10:12 pm »
so, how was it? ::)
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Offline studz

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Re: Edexcel PHYSICS Doubts
« Reply #714 on: June 06, 2011, 05:24:08 pm »
it was great  ;) ;D
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Offline wakemeup

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Re: Edexcel PHYSICS Doubts
« Reply #715 on: June 20, 2011, 12:17:15 pm »
I'm pretty much completely lost on Q16 of Jun 10 paper 4. Would really appreciate it if someone could clearly explain parts bi, ci and cii.

Also, in Q13b, how are we supposed to estimate the radius if we don't have any reference in the diagram? 
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Offline Romeesa-Chan

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Re: Edexcel PHYSICS Doubts
« Reply #716 on: June 20, 2011, 12:17:31 pm »
Doubts:

*A 47micro F capacitor is charged to a pd of 15V and then discharged through a 100k Ohm resistor. How long does it take for half of the energy stored in the capacitor to have dissipated in the circuit?

*A beam of electrons enters a region of uniform electric field, moving at right angles to the field and is deflected into a circular path.
Draw a diagram to show the path of electrons, including directions of the electron velocity 'v' and the magnetic field 'B'.
« Last Edit: June 20, 2011, 12:56:57 pm by Hermione Jean Granger »
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Offline Romeesa-Chan

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Re: Edexcel PHYSICS Doubts
« Reply #717 on: June 20, 2011, 12:31:15 pm »
Quote from: wakemeup on June 20, 2011, 12:17:15 pm
I'm pretty much completely lost on Q16 of Jun 10 paper 4. Would really appreciate it if someone could clearly explain parts bi, ci and cii.

Also, in Q13b, how are we supposed to estimate the radius if we don't have any reference in the diagram?  

I am lost in 13b myself too. :(

Ok, Q16:

bi) Capacitor stores charge, as charge flows in during the charging process, pd is also formed.
If the voltage is constant, the capacitor will not discharge. The graph is during the charging process. Hence, pd is constant.
(remember: during discharging process, pd falls.)

ci) Use E= 1/2*C*V^2
(take voltage value from the graph)

cii) Compare the graph with the previous one and see the change in voltage value. (pd decreases)
Capacitor is initially charging from power supply then the capacitor is discharging exponentially.
(remember: the changing position of switches causes the discharge process, instead here. . . we added a power supply)

I hope that's clear. :)
« Last Edit: June 20, 2011, 12:35:16 pm by Hermione Jean Granger »
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Offline viktress

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Re: Edexcel PHYSICS Doubts
« Reply #718 on: June 20, 2011, 01:31:57 pm »
Hey guys could you help me out with this question I've trying to crack for almost a day now? It's from the Edexcel a2 revision guide (physics).

A runner of mass 65kg is running a circular running track at a sped of 5.0m/s. The magnitude of the runner's change in momentum from starting to end position after half a revolution is
A. 0 N s
B. 325 N s
C. 460 N s
D. 625 N s

The correct answer according to the book is D, but I just can't seem to be able to get i. Could you please try to work it out? Thanks!
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Offline Romeesa-Chan

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Re: Edexcel PHYSICS Doubts
« Reply #719 on: June 20, 2011, 02:43:09 pm »
Quote from: viktress on June 20, 2011, 01:31:57 pm
Hey guys could you help me out with this question I've trying to crack for almost a day now? It's from the Edexcel a2 revision guide (physics).

A runner of mass 65kg is running a circular running track at a sped of 5.0m/s. The magnitude of the runner's change in momentum from starting to end position after half a revolution is
A. 0 N s
B. 325 N s
C. 460 N s
D. 625 N s

The correct answer according to the book is D, but I just can't seem to be able to get i. Could you please try to work it out? Thanks!


The last option D is wrong- suppose to be 650N.

F*t= m*v => change in momentum

Think of half a circle.

at the "top" it is travelling ------->>> at p=mv = 325Ns

at the "bottom" it is travelling <<<------- at p=mv = -325Ns

Therefore the change in momentum is = 325 - (-325) = 650Ns
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