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Physics: Post your doubts here!

daredevil

daredevil

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periyasamy said:
Sorry guys i just google searched n saw this picture but i dont reallly understand why it is saif that the force acting for moon is opposite for the force acting on earth.Anybody can help me.Thanks.
Click to expand...
i think it is the fact that Earth's gravitational force is acting on the moon which is towards the center of the Earth (direction) whilethe moon's gravitational force acts on the Earth and is towards the center of the moon .... thus being opposite. just a theory... i'm not confirm.
 
daredevil

daredevil

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hellangel1 said:
Help
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s11_qp_21.pdf
please someone tell how to do question 5 part b..
Click to expand...
maximum possible I2 is possible when the potentiometer is set at its highest resistance value such that no current passes through the potentiometer... ALL the current of the circuit is passing through the fixed resistor as I2.
The least I2 is when the potentiometer is set at its least value. Calculate the current passing through the potentiometer and the fixed resistor relatively. Remember that the Voltage is same for both ; the potentiometer as well as the fixed resistor.

If you don't get it then tell me :)
 
H

hellangel1

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daredevil said:
maximum possible I2 is possible when the potentiometer is set at its highest resistance value such that no current passes through the potentiometer... ALL the current of the circuit is passing through the fixed resistor as I2.
The least I2 is when the potentiometer is set at its least value. Calculate the current passing through the potentiometer and the fixed resistor relatively. Remember that the Voltage is same for both ; the potentiometer as well as the fixed resistor.

If you don't get it then tell me :)
Click to expand...
Thanku so much :)
 
Hassan Ali Abid

Hassan Ali Abid

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Can anyone please ans me why the magnitute of induced emf increases in the coil when it is rotated when it is places beside a current carring wire ? Do more magnetism flux linkage are cut when coil is rotated ?
 
M Ahmed Khan

M Ahmed Khan

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#h
XPFMember said:
Hi everyone, AsSalamoAlaikum Wr Wb...

To get things organized in a better way, I am making this thread. As othewise, some queries remain unanswered!

So post your PHYSICS doubts in this thread. InshaAllah other people here will help me and you all. :D ;)

NOTE: If any doubts in the pastpapers, please post the link! You can find links here!

Any Physics related notes and links will be added here in this post. Feel free to provide the links to your notes around the forum, or any other websites! :)
Thanks!
Jazak Allah Khair!

Physics Notes:

Some links & Notes - by destined007

As physics p1 MCQS YEARLY Solved [explaination]
Physics Practical Tips - by arlery

Notes for A2 Direct Sensing (Applications) - shared by sweetiepie

Physics Summarised Notes (Click to download)

AS and A-Level Physics Definitions

A2: Physics Revision notes - by smzimran

Paper:5 Finding uncerainty in log - by XPFMember

Physics Paper 5 tips - by arlery

Physics Compiled Pastpapers: <Credits to CaptainDanger for sharing this..>

Here are the compiled A level topical Physics questions in PDF form...

Paper 1 : http://www.mediafire.com/?tocg6ha6ihkwd

Paper 2 & Paper 4 : http://www.mediafire.com/?g65j51stacmy33c

(Source : http://www.alevelforum.com/viewtopic.php?f=15&t=14)[/quote
XPFMember said:
Hi everyone, AsSalamoAlaikum Wr Wb...

To get things organized in a better way, I am making this thread. As othewise, some queries remain unanswered!

So post your PHYSICS doubts in this thread. InshaAllah other people here will help me and you all. :D ;)

NOTE: If any doubts in the pastpapers, please post the link! You can find links here!

Any Physics related notes and links will be added here in this post. Feel free to provide the links to your notes around the forum, or any other websites! :)
Thanks!
Jazak Allah Khair!

Physics Notes:

Some links & Notes - by destined007

As physics p1 MCQS YEARLY Solved [explaination]
Physics Practical Tips - by arlery

Notes for A2 Direct Sensing (Applications) - shared by sweetiepie

Physics Summarised Notes (Click to download)

AS and A-Level Physics Definitions

A2: Physics Revision notes - by smzimran

Paper:5 Finding uncerainty in log - by XPFMember

Physics Paper 5 tips - by arlery

Physics Compiled Pastpapers: <Credits to CaptainDanger for sharing this..>

Here are the compiled A level topical Physics questions in PDF form...

Paper 1 : http://www.mediafire.com/?tocg6ha6ihkwd

Paper 2 & Paper 4 : http://www.mediafire.com/?g65j51stacmy33c

(Source : http://www.alevelforum.com/viewtopic.php?f=15&t=14)
Click to expand...
When a body accelerates from rest would the net resultant force acting on it remain constant or is it going to increase
Click to expand...
 
Faizan Muhammmad

Faizan Muhammmad

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View attachment 34015
Circuit as shown in figure :)

Switch closed what happens?
Since capacitor is charging for some time all current falls on it but in the end does the bulb light up?
And does it light up continuosly or the capacitor discharges in process and hence the bulb blinks ?

Thanks in advance :)
 
B

BreakingBad

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GlitteringLights said:
Can anyone plz explain ques 4 part (c) please? thank you
http://olevel.sourceforge.net/papers/9702/9702_s13_qp_43.pdf
Click to expand...
Use the equation in the previous part to calculate the speed 'required' to reach the stationary sphere.

v = (2qV/m)^1/2

V is given as 470V, q/m (specific charge) is given as 9.58 * 10^7

Hence,

v = (2 * 9.58 * 10^7 * 470)^1/2 = 3*10^5

The 'required' speed to reach the sphere is 3*10^5. However, the speed with which the charge is traveling is only 2.5*10^5. Therefore, we can say that the charge will be deflected (both charges are positive) before it can reach the sphere.
 
B

BreakingBad

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Hassan Ali Abid said:
Can anyone please ans me why the magnitute of induced emf increases in the coil when it is rotated when it is places beside a current carring wire ? Do more magnetism flux linkage are cut when coil is rotated ?
Click to expand...
In comparison to what? Try being a little clearer. I might be able to help you then.
 
GlitteringLights

GlitteringLights

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BreakingBad said:
Use the equation in the previous part to calculate the speed 'required' to reach the stationary sphere.

v = (2qV/m)^1/2

V is given as 470V, q/m (specific charge) is given as 9.58 * 10^7

Hence,

v = (2 * 9.58 * 10^7 * 470)^1/2 = 3*10^5

The 'required' speed to reach the sphere is 3*10^5. However, the speed with which the charge is traveling is only 2.5*10^5. Therefore, we can say that the charge will be deflected (both charges are positive) before it can reach the sphere.
Click to expand...

thank you! :)
 
B

BreakingBad

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1357911 said:
@Kim Shaw
Can u please help me with the following questions.
http://olevel.sourceforge.net/papers/9702/9702_s13_qp_11.pdf
Q-18
Q-17
Q-16
Q-11
Q-8
id be really grateful
Click to expand...
Q8
The time when the express train crosses the goods train will be the time when both of them have traveled the same distance.
Distance traveled by goods train = speed * time = 10t
Distance traveled by express train = ut + 1/2at^2 = 1/2at^2

u = 0 (express train starts from rest) and t cancels:

1/2at = 10
at = 20 (acceleration = 0.5)
t = 40s

Answer is D

Q11:

The collision is inelastic. Masses are added on the RHS:

m1v1 + m2v2 = (m1 +m2)v
v2 = 0, so:

2 * 3 = (2 + 1) v
v = 2
KE lost = Initial KE - Final KE = 0.5m1v1^2 - 0.5(m1 + m2)v^1/2
= 0.5*2*3^2 - 0.5*3*2^2 = 3 J

Answer is D

Q16:

Since the tension T in the cable alone is countering the other forces to keep the trapdoor in equilibrium, it is the largest. The only option with T being maximum is C, so the answer is C.

Q17:

v = (2gh)^1/2
HEIGHT IS 0.72 NOT 0.8! Measure from the base of the ball. Diameter is 0.08. We have to subtract that.

Use 1/2mv^2 = initial KE to calculate mass.

u = (2gh)^1/2
Again, height is 0.45-0.08 m.
KE after impact = 1/2mu^2 = 0.39 J

Answer is C

Q18:

P = E/t
P = (1/2mv^2)/t [m = density p * volume V]
P = (1/2pVv^2)/t [Vol = Area A * length s]
P = (1/2pAlv^2)/t [l/t = speed v]
P = 1/2Alv^3

Substitute values, Answer is B.
 
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