Qualification > Sciences
Physics Paper4
ruby92:
o/n 2010 variant 41 question 1 c (i) and (ii)
Same paper variant 43 question 3 b (i) and (ii)
Sue T:
hope im answering the ryt one :
paper 41 - 1ci) you have a gravitational field due to the earth, attracting any mass within its field to the left hand side of ur ppr , and you have another (smaller) gravitational field due to the moon attracting masses to your right hand side of th paper - (its smaller cuz the moon is smaller- simple) now at some point wont the resultant force exerted on unit mass, somewhere between the two planets, be equal and opposite? so thats why the grav field strength is zero
ii) grav. field strength = GM/r2 where M is the mass of the thing causing the field
so if the at a certain distance r from the centre of the earth - the grav field strengths of both planets are equal we form this eqn:
GMearth = GMmoon
_____ ____________
r2 (60RE-r)2
cancel the Gs and put in the masses - eventually you'll get ans answer in terms of RE
Sue T:
paper 43 - 3bi) for cylinder X they gave you an eqn : x= -4.0Cos(220t)
now the phase diff for cylinder Y is 2pie/3
so the eqn for cylinder Y becomes : x= -4.0Cos(220t + 2pie/3) {everything else like freq and amplitude are same}
now the instant theyre talkin bout is wen x= -4 (you can see from th fig that cylinder X is in its lowest position where x=-4) so putting it in th eqn we get:
-4 = -4Cos(220t)
therefore 220t=0
put that in ur eqn for cylinder Y - you get its displacement at that instant :
x=-4.0Cos( 0 + 2pie/3 )
you get x=2
so draw it 2cm above AB
the next one is th same - th arrow direction is diff bcuz it has already done half a cycle (pie) and is continuing downwards ---> (as in 4pie/3 is larger than pie)
hope its clear - i got stuck here too a couple of days ago
basoom16:
hello can u help me with physics paper 42 o/n 2009
1b why is the radius taken as 2.86x10^7 insted of 2.22x10^7
thank you
ruby92:
--- Quote from: basoom16 on May 08, 2011, 06:41:07 pm ---hello can u help me with physics paper 42 o/n 2009
1b why is the radius taken as 2.86x10^7 insted of 2.22x10^7
thank you
--- End quote ---
In the equation F=GMm/r^2
r is taken from the center of mass. So r=Radius of earth+Distance of orbit from earths surface.
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