Physics: Post your doubts here!

[Hussnain]

22 23 or 21?

sorry
23

 

[Hussnain]

DAMPING
Slightly under critical damping??
Ways to increase or decrease damping?
Advantages and disadvantages of damping?

 

[smartangel]

can someone please explain Q8 iii
http://www.xtremepapers.com/papers/...and AS Level/Physics (9702)/9702_s07_qp_4.pdf

 

[JD REBORN]

be more specific like paper and question part

3(c)
The useful work done is 600J and u have to find work done against resistance.Now in b u calculated loss in in kinetic energy and gain in potential energy.So
Useful work done-work done against resistance=Gain in potential +gain in kinetic enrgy
600-W=1170-1240(kinetic energy will be negative because it is lost)
W=670 J.
The part (ii) requires the formula
W=Force * distance moved in the direction of force.Dont make the mistake of using 1.8m because it is the vertical distance and bicycle is moving at an angle up the slope.So u know the value of W which is 670 and distance will be the one u calculated in (a) part because friction is acting for this distance.
670=F*39
F=17 N
Q6(ii)
Man which part a.b.c or d??

 

[smartangel]

Q8 iii and 10..can someone draw tthe graph for me please? http://www.xtremepapers.com/papers/...and AS Level/Physics (9702)/9702_s07_qp_4.pdf

 

[Hussnain]

Accuracy and Precision?

 

[confused123]

Accuracy and Precision?

?
Accuracy is when the measured value is closer to the actual value such as speed of sound in air is 330 m/s. if you come up with a measurement closer to it then its accurate. if u draw a graph there should be sharp peak closer to actual value.
precision is when measurements are close enough to the mean of all the measurements taken. the graph is spread evenly around the mean value. all measurements have a very less difference from the mean value. if a measurement is precise it doesn't mean it has to be accurate as well.

correct me if m wrong. tnx

 

[hassam]

can somebody tell me..a situation where resonance is useful and one where its is harmful....pls write a expplained sentence....

 

[smzimran]

can somebody tell me..a situation where resonance is useful and one where its is harmful....pls write a expplained sentence....

Aoa wr wb,
Harmful:
The operation of the engine of a vehicle causes a periodic force on the parts of the vehicle, which can cause them to resonate. For example, at particular frequencies of rotation of the engine, the mirrors may resonate. To prevent excessive vibration, the mountings of the mirrors provide damping.

Useful:
Musical instruments rely on resonance to amplify the sound produced.The sound from a tuning fork is louder when it is held over a tube of just the right length, so that the column of air resonates.

 

[smartangel]

http://www.xtremepapers.com/papers/...and AS Level/Physics (9702)/9702_w07_qp_4.pdf
Q11 a. why is a country divided into a number of cells?

 

[smartangel]

also, 11 a (ii) of this paper http://www.xtremepapers.com/papers/...and AS Level/Physics (9702)/9702_s08_qp_4.pdf

 

[smzimran]

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w07_qp_4.pdf
Q11 a. why is a country divided into a number of cells?

Aoa,
See the application booklet page 41-42

 

[smzimran]

also, 11 a (ii) of this paper http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s08_qp_4.pdf

There is no 11(a)(ii) !
if u r talking abt part (b) i would advise you to learn the answer frm the m.s
this question has been repeated many times!

 

[smartangel]

There is no 11(a)(ii) !
if u r talking abt part (b) i would advise you to learn the answer frm the m.s
this question has been repeated many times!

there is Q11 a (ii) :S June 08 paper 4. http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s08_qp_4.pdf

 

[smzimran]

there is Q11 a (ii) :S June 08 paper 4. http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s08_qp_4.pdf

Oh, ok!
Here goes:
1. the amplitude:
In FM modulation, amplitude is unchanged and it will be the same amplitude of carrier wave, which is 6.0 V
So, variation of amplitude = 0

2. the frequency:
frequency variation = frequency deviation of the carrier wave * amplitude of information signal
frequency variation = 20 * 1.5 = 30 kHz

frequency of carrier wave was 500 kHz
Limits = (500 - 30)kHz and (500 + 30)kHz
= 470 kHz and 530 kHz

This change between frequencies (470 kHz and 530 kHz) happens 8000 times in one second [frequency of information signal = 8 kHz]

 

[smartangel]

in Q 11 b(ii)..how do we calculate the frequency of the information signal?
http://www.xtremepapers.com/papers/...nd AS Level/Physics (9702)/9702_w09_qp_42.pdf

 

[sweetiepie]

HOPE THIS HELPS EVRYONE

 

[hmlahori]

No, it isn't related to Centripetal force - you're not expected to know about it in an AS Level paper. B should be the answer, because that is the resultant of normal force and friction force on the tyre. Force of friction is in the same direction as car's motion because the tyre must be rotating in a clockwise direction.

Ohh ok i get it now thanks!

 

[XPFMember]

june 2002 q4b) at max displacement the p.e is maximum. and at mean position it is zero. so the graph will be at max at max displacement. but it will be all above xaxis because energy can not be negative.
c) t = 2pie * sqr root of mass / sqr root of 'k'
when mass decreases time period also decrease.
sorry i dont knw abt amplitude

aoa
is it like a full wave rectification graph..? right?

 

[XPFMember]

nov 2002) when 1/2 f0 is impressed then the time period will be 2T. so every impulse is after 2 oscillations. means alternate oscillations are energized. so there is continuous increase of amplitude at every impulse.

What exactly am I supposed to write? :s do i write this all ^