Physics: Post your doubts here!

[bamteck]

First of all find the resistance of the individual resistor which is 38.4
First is open close close so
No current as the first switch is open so no power
then Close Close open
Current passes but as Switch two is open so Current bypasse the resistor B so the resistance is not taken into account of B see because the current has an easier route so we say it is a short circuit so when we take the effective resistance it wiill only be 38.4 as Switch 3 is openso
p=V^2/Rand we get 1500 watts
In Third Case it is Close CLOSE CLOSE
Now againn the current bypasse resistance B a short circuit occur so we take the resistance of A and C in parrallel as in the circuit.
Hope you get the idea if not please feel free to ask please

Thanks mate

 

[axetreme.O]

Uhm, this actually gave me a strike.

okay, for light to have force it must have mass and acceleration. because force=m*acc.
but that is not the case here, why? let's see.
the best way to describe force of light is the absorption and emission of light. when light is absorbed so is it's energy and momentum the same goes for the emission of light. for light to have a force, mass is not necessary but it must have momentum. (i don't get more than that ) i think to go further quantum mechanics is what's required.

thank you but
was that a yes or no?

 

[hussamh10]

is there nobody to help me..im begging

Read from a book its best i think gieger marson smthng like that exp where they find that nucleus has empty spaces and yeah the experiement in which lead ,paper and wooden block are used to block Alpha Beta and Gamma particles ...( Read from a Book)

 

[InnocentAngel]

Please buddies help me : http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w05_qp_2.pdf
Answer : Velocity is a vector quantity , so it has both direction and magnitude. Direction must be changing so must be accelerating.
Number 3 . Part (b) .
In mathematics we've always learnt that when velocity is constant acceleration is zero . Then why in this question does this theory not apply ?
Please help me.
Thanks in advance.

 

[axetreme.O]

Please buddies help me : http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w05_qp_2.pdf
Answer : Velocity is a vector quantity , so it has both direction and magnitude. Direction must be changing so must be accelerating.
Number 3 . Part (b) .
In mathematics we've always learnt that when velocity is constant acceleration is zero . Then why in this question does this theory not apply ?
Please help me.
Thanks in advance.

-First of all it is not at all mentioned in the question that the velocity is constant hence you cannot assume that the acceleration is zero.
-Furthermore as the path of the stone is circular its velocity keeps changing due to the change in direction.(velocity is a vector quantity and has a particular direction).
-Acceleration- as you know is; change in velocity upon time taken. And as there is a change in velocity the object has to posses acceleration.

 

[Silent Hunter]

http://www.xtremepapers.com/papers/...nd AS Level/Physics (9702)/9702_w11_qp_23.pdf

Q4(iv) 3 ... why do they do V = 2.1 + (I × 1.8) why not - as in the formula?

 

[caro24]

Read from a book its best i think gieger marson smthng like that exp where they find that nucleus has empty spaces and yeah the experiement in which lead ,paper and wooden block are used to block Alpha Beta and Gamma particles ...( Read from a Book)

do you have any references

 

[emkay]

thank you but
was that a yes or no?

i discussed this with my teacher yesterday and he said No, the light cannot have a force on any particle. All that it can do is have its light absorbed and emission-ed where its energies are converted from one form to another.

 

[emkay]

Thanks a lot man
But why n the question, its says 'use your answer in (c)' ? oO'

that is because (d) is related to change in kinetic energies and since you found the velocity of ball S after the collision in (c). it is a basically a hint to compare kinetic energies of ball B and ball B+S before and after the collision. Remember change in kinetic energy is of an system. (that is why here, we used the Ek before collision of ball B and Ek after collision for ball B+S)

 

[hussamh10]

do you have any references

Anycambridge endorsed book...

 

[Beca1206]

can someone please help me with question 5 d ii.) i dont get what the mark scheme says...
question : http://www.xtremepapers.com/papers/...nd AS Level/Physics (9702)/9702_w11_qp_21.pdf
mark scheme : www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w11_ms_21.pdf

 

[hussamh10]

http://www.xtremepapers.com/papers/...nd AS Level/Physics (9702)/9702_s11_qp_23.pdf
Q2 draw the vector diagram plz help urgent....

 

[shikha95]

Please buddies help me : http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w05_qp_2.pdf
Answer : Velocity is a vector quantity , so it has both direction and magnitude. Direction must be changing so must be accelerating.
Number 3 . Part (b) .
In mathematics we've always learnt that when velocity is constant acceleration is zero . Then why in this question does this theory not apply ?
Please help me.
Thanks in advance.

It says that the stone has constant SPEED not velocity... if you check it out, the direction is constantly changing.. even though magnitude must be the same...

 

[bamteck]

that is because (d) is related to change in kinetic energies and since you found the velocity of ball S after the collision in (c). it is a basically a hint to compare kinetic energies of ball B and ball B+S before and after the collision. Remember change in kinetic energy is of an system. (that is why here, we used the Ek before collision of ball B and Ek after collision for ball B+S)

Ohh ! Thanks You're great

 

[aiskw1]

can someone please help me with question 5 d ii.) i dont get what the mark scheme says...
question : http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w11_qp_21.pdf
mark scheme : www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w11_ms_21.pdf

for 5dii) for a circuit to have infinite resistance, there must be ends of a wire that are not touching each other, and are at a short distance away. Therefore, no current flows. ( I'm not sure about this but it's something along this context)

therefore the power must be zero

P=VI
P=I^2R etc etc

 

[hussamh10]

It says that the stone has constant SPEED not velocity... if you check it out, the direction is constantly changing.. even though magnitude must be the same...

It says Constant SPEED not velocity the direction is changin

 

[geek101]

can someone please explain the graph in 2b

qp : http://olevel.sourceforge.net/papers/9702/9702_s12_qp_22.pdf

ms : http://olevel.sourceforge.net/papers/9702/9702_s12_ms_22.pdf

thanks

 

[shikha95]

It says Constant SPEED not velocity the direction is changin

why did you say exactly what I said?

 

[Sriyog Sharma]

Hey guys , check this question real quick.
How is force related with velocity ? What happens to Force if velocity increases or decreases ?

 

[Sriyog Sharma]

Anyone has the projectile formulas for AS physics ? I would appreciate if yo provide me the formulas of both horizontal and vertical component / help guyss :/