Physics: Post your doubts here!

[anahita16]

Seriously...if, If, IF anyone did know that, wud he/she dare post it? Exams wud be meaningless then
Better ask wat MAY come up, that's more likely to give us an answer!

GUESS there'd be an electricity practical and oscillation one!!! that's wat may come up!! Just a few more hours left posting.php?mode=quote&f=26&p=136983#
Good luck to everyone
posting.php?mode=quote&f=26&p=136983#

few hours for you but 2 weeks for me 8)

I fnk electricity n mechanics component. so electricity is common here...

 

[ambitious1]

Hey,
Can someone help me out with physics, paper5 O/N 2007 Q1, by drawing the diagram? Cause i"m not pretty sure of it.
Thanks

 

[Abdulrab]

http://www.xtremepapers.com/CIE/Interna ... s10_er.pdf please explain q 7 c(ii) thanku in advance !!

 

[rz123]

^attach the correct link !

 

[Abdulrab]

sorry this is the correct link http://www.xtremepapers.com/CIE/Interna ... _qp_21.pdf Q 7 c


http://www.xtremepapers.com/CIE/Interna ... _qp_13.pdf Q 3,16, 29,34 thanku waiting for the answers with explanation

 

[rz123]

The mass of proton is given on the data sheet. simply multiply it by the mass number of Uranium 238. (mass of neutron and proton equal)
7c ii) mean density = mass / volume mass already known form part i) , volume of the sphere (atom) formula applied. 4/3 pie r ^3 to calculate the volume, substitute in the equation. . . . so easy use ms. :|

q.16) water has a higher density then ice so density will increase and the atoms spacing will decrease as ice is contracting, pressure is applied to it although the volume remains same.

34. D as ammeter is not connected in series with any resister, it is given a separate path from P to Q hence max current will flow.

 

[Abdulrab]

wat abt 3 and 34 ??
how can the density of water can be greater than ice like is there any concept behind it !!!

thanks alot

 

[rz123]

welcome ,i can't figure out what will be the wavelength in 3 , but dre has to be some way u need to calculate the total waves divided by total distance covered then multiply length of one wave by time base setting, nd taking period inverse,
34. no solid concept but the point charge is already in the field so no work done in moving it from p to q. it doesn't need to be brought up from infinity its already in the electric field so no work done. 0 hence option A.

Why can't be? :/ its a natural special property of water, it has a higher density that's why ice floats marine animals survive bla bla. Wikipedia it for further detail. use the thanks button at the right hand corner

 

[Abdulrab]

thnku bro but i want to ask when inside in an electric field a point charge moves a particular distance so isnt a work done as the force is constantly acting on it ??

 

[rz123]

^^its 29th mcq not 34 i got it somehow ! E is same through out and r as well so no change in the distance and force acting on the charge when it travels from P to Q, hence work done remains zero ! yeah hurray!! :/

 

[ambitious1]

Why values of gravitational potential are always negative whereas values of electric potential may be positive or negative?
what other reasons other than 1-gravitational forces are always attractive & 2-electric forces can be attractive or repulsive. ?
thanks

 

[grumpy]

@ambitious 1 this is only for you.

you know the inverse square law for great distances 1/x*2 is zero so enery is zero.
when a body is attracted it losses its potential to attract other objects towards itself for this reason its potential to attreact objects becomes less than the original value and original value is zero anything less than zero will be negative.
i have now explained your point of attracting field.

but in electrical case positive charge exerts an outward force on the test charge.(test charge is always positive taken as standard) so repulsion occurs . if the object (charge) comes close to +ve charge from infinity than its working against the force so additional force is required for force energy is also required. so the required energy is greater than the original value which is zero so in case of positive charge energy is taken to be positive.

IF YOU LIKED MY EXPLANATION AND UNDERSTANDS IT. SAY THANKS TO ME.

 

[Abdulrab]

http://www.xtremepapers.com/CIE/Interna ... _qp_23.pdf Q 5a(i) Q 7a (ii) b(iii)

 

[rz123]

5 a i) fig 5.2 as the spring is at at the greatest height as compared to the others spring, g.p increases with the height.

7a ii ) 1. F = E q , 2. distance is L ( the plate length) speed is v ) so L / v= t formula to be used.

7 b iii) my take is that the linear momentum does not obeys as the particles direction i.e velocity is continuesly changing as it moves between the plates. p is not same as before entering the plates. can't get the other scenario which says it obeys the law!!!!

 

[Abdulrab]

in 5a(i) fig 5.3 spring has the grearest height so wouldnt it hav the max potential energy ???

 

[grumpy]

no way try reading the question more thoroughly

 

[rz123]

^^no greatest height from the floor i mean. 5.2 being raised vertically to achieve its unextended length so highest g.p acting on it...others springs are closer to the floor

 

[rz123]

in 5a(i) fig 5.3 spring has the grearest height so wouldnt it hav the max potential energy ???

dude use the latest Cambridge endorsed physics book , it really make easier to understand the concepts. i will highly recommend it !

 

[Abdulrab]

dude i dont hav it if u hav a link on it please post it or any note on it !! thnks

 

[rz123]

no its not on website. u gotta buy it from book store! notes hmm find the threads here for physics notes. u will get plenty. Search!