IGCSE/GCSE/O & A Level/IB/University Student Forum

Qualification => Subject Doubts => GCE AS & A2 Level => Sciences => Topic started by: nid404 on July 12, 2010, 04:48:44 pm

Title: Physics help A2
Post by: nid404 on July 12, 2010, 04:48:44 pm
 June 07 Q3

Can someone please explain part b and c

Thanks  :)
Title: Re: Physics help A2
Post by: nid404 on July 12, 2010, 04:55:28 pm
I have a test tom...please? :P
Title: Re: Physics help A2
Post by: *Hope* on July 12, 2010, 05:31:43 pm
I have a test tom...please? :P
OMG!! am reallllyyy sorry I can't help since I did only AS-level phy :-\
and u started A2 already?
walla am sorry..but I'll pray for u from my heart..insA u'll get it and do well :)
Title: Re: Physics help A2
Post by: nid404 on July 12, 2010, 05:32:22 pm
lol thanks :)

If you know anyone who can help...please direct them here  :-[
Title: Re: Physics help A2
Post by: Nobody on July 12, 2010, 05:58:32 pm
oh! XENA needs some help?!!!!...the one who helps everyone..
hehe...Time for some action..i'll try to solve it.
it's paper 4 right.?
Title: Re: Physics help A2
Post by: nid404 on July 12, 2010, 05:59:32 pm
yup yup paper 4  ;D
Title: Re: Physics help A2
Post by: Light on July 14, 2010, 12:59:38 pm
3a) field strength is equal to the negative potential gradient.(its the concept u need to know)
b)find the area under graph by counting boxes.more than half counted as 1 box,less than half box not counted.calculate area of a box multiply with no of boxes.
c)use kinetic energy equals to electric potential energy.½mv2 = qV
½ × 9.1 × 10–31 × v2 = 1.6 × 10–19 ×  530(u should get this value in b)
v = 1.37 × 107 ms–1
d)the gradient of graph indirectly shows the acceleration.d=0 ,it is steepest at that point.
from graph ,acceleration decreases(negative gradient) and increases(positive gradient).minimum at 4cm.
Title: Re: Physics help A2
Post by: nid404 on July 14, 2010, 03:18:55 pm
3a) field strength is equal to the negative potential gradient.(its the concept u need to know)
b)find the area under graph by counting boxes.more than half counted as 1 box,less than half box not counted.calculate area of a box multiply with no of boxes.
c)use kinetic energy equals to electric potential energy.½mv2 = qV
½ × 9.1 × 10–31 × v2 = 1.6 × 10–19 ×  530(u should get this value in b)
v = 1.37 × 107 ms–1
d)the gradient of graph indirectly shows the acceleration.d=0 ,it is steepest at that point.
from graph ,acceleration decreases(negative gradient) and increases(positive gradient).minimum at 4cm.

a little late...but thanks :) + rep
Title: Re: Physics help A2
Post by: Ghost Of Highbury on July 28, 2010, 02:44:40 pm
A thermometer can be read to an accuracy of ±0.5 °C. This thermometer is used to measure a
temperature rise from 40 °C to 100 °C.
What is the percentage uncertainty in the measurement of the temperature rise?
A 0.5 % B 0.8 % C 1.3 % D 1.7%
Title: Re: Physics help A2
Post by: Alpha on July 28, 2010, 02:59:03 pm
A thermometer can be read to an accuracy of ±0.5 °C. This thermometer is used to measure a
temperature rise from 40 °C to 100 °C.
What is the percentage uncertainty in the measurement of the temperature rise?
A 0.5 % B 0.8 % C 1.3 % D 1.7%

I'm not sure... Engraved or Astar can check.  :-\

But still.

Rise = 60 °C

+ 0.5 or -0.5 => Interval = 1 °C

% uncertainty = 1/60 °C *100% = 1.7%

Have the MS?
Title: Re: Physics help A2
Post by: Vin on July 28, 2010, 03:11:14 pm
I think it should be B. 0.8% :-\
Title: Re: Physics help A2
Post by: nid404 on July 28, 2010, 03:27:38 pm
should be 1.7%
Title: Re: Physics help A2
Post by: Freaked12 on July 28, 2010, 03:31:29 pm
Should be B

0.5/60
Title: Re: Physics help A2
Post by: nid404 on July 28, 2010, 03:33:24 pm
Should be B

0.5/60

It's measuring a change.

100 +- 0.5 - 40 +-0.5

the total uncertainty in the final ans will be +- 1  as far as my knowledge goes.

Title: Re: Physics help A2
Post by: Vin on July 28, 2010, 03:41:54 pm
It's measuring a change.

100 +- 0.5 - 40 +-0.5

the total uncertainty in the final ans will be +- 1  as far as my knowledge goes.



oooh yeah right, I get it now. Thanks. :)
Title: Re: Physics help A2
Post by: nid404 on July 28, 2010, 03:52:42 pm
oooh yeah right, I get it now. Thanks. :)

That's what I think it is...anytime (:
Title: Re: Physics help A2
Post by: Alpha on July 29, 2010, 08:35:16 am
Adi has the MS?
Title: Re: Physics help A2
Post by: nid404 on July 29, 2010, 02:12:26 pm
Adi has the MS?

1.7 is right
Title: Re: Physics help A2
Post by: Alpha on July 29, 2010, 02:15:24 pm
1.7 is right

Sure? When I saw it was Physics, I became unsure... lol

By the way, thanks.  ;)
Title: Re: Physics help A2
Post by: nid404 on July 29, 2010, 06:30:06 pm
Anytime :)
Title: gravitation ques prob!!
Post by: sizbeauty on September 19, 2010, 05:48:01 pm
Q1,find the speed of the satellite which orbitz the moon near the moon's curface?
what is the kinetic energy per unit mass of the satellite?
(radius of moon: 1.74*10^6,mass of moon: 7.35*10^22)

Q2,astronomical observationz show the centre of mass of the earth-moon system is 4.7*10^6 m frm the centre of the earth.the distance b/w the centre of the earth n the moon is 384.4*10^6 m.find the mass of the moon M in terms of the mass of the earth E.
explain why both earth n moon must rotate about their common centre of mass,rather than the moon abot the centre of mass of the earth.
Title: Re: gravitation ques prob!!
Post by: nid404 on September 19, 2010, 05:59:03 pm
Q1,find the speed of the satellite which orbitz the moon near the moon's curface?
what is the kinetic energy per unit mass of the satellite?
(radius of moon: 1.74*10^6,mass of moon: 7.35*10^22)

Q2,astronomical observationz show the centre of mass of the earth-moon system is 4.7*10^6 m frm the centre of the earth.the distance b/w the centre of the earth n the moon is 384.4*10^6 m.find the mass of the moon M in terms of the mass of the earth E.
explain why both earth n moon must rotate about their common centre of mass,rather than the moon abot the centre of mass of the earth.

Mass of the satellite? :\

Do you have the entire question? Is it from a past paper?
Title: Re: Physics help A2
Post by: sizbeauty on September 19, 2010, 06:13:27 pm
this is the entire ques!!
itz frm unsolved topical pastpaperz,this one is frm year Nov88/p2/Q3.
do u have dese pastpprz??
Title: Re: Physics help A2
Post by: nid404 on September 19, 2010, 06:16:58 pm
In the first question, the gravitation pull provides the necessary centripetal force. So you equate the two

GMm/ r2= mv2/r

You get v.

The second half, I don't really get it. The mass of the satellite ain't mentioned...I can't figure that.
Title: Re: Physics help A2
Post by: sizbeauty on September 19, 2010, 06:19:30 pm
ok np!! :)
thanx for de help,you r the saver!!  :)
Title: Re: Physics help A2
Post by: nid404 on September 19, 2010, 06:21:24 pm
The second question. At 4.7*10^6 m frm the centre of the earth. the gravitational pull on any objects would be 0 apparently.

So.

GM/ (4.7*10^6)2= GM2(mass of the moon)/ (384.4*10^6 - 4.7*10^6)2

You get M2.

I don't get the second half of this one either :\
Title: Re: Physics help A2
Post by: sizbeauty on September 19, 2010, 06:27:41 pm
hehe itz ok!!  ;D
i ll let u knw de scnd part of both dese ques if i becum smart enough to get thm frm ma teacher'z xplanation!! :P
thanx alot once again!! :)