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AS Physics P1 MCQs Preparation Thread.

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34 first... r is directly propotional to length/cross sectional area... for X.. R= L/(pie)(D/2)^2 ----. R=4L/pie D^2
for Y.. R=2L/(pie)D^2 ----- R= 2L/(pieD^2)
simplify it and you will have the A as answer...
one qs, y cant we simply use 'pid' forr the area!!! its the same as pi( d/2)^2 ??
 
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one qs, y cant we simply use 'pid' forr the area!!! its the same as pi( d/2)^2 ??
if the answer is same than u cn use...:p but wire is supposed to have a circular shape... and its cross sectional area is designated by pi(d/2)^2...
 
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View attachment 12098How is the answer D? If the strain increases wont the length decrease(strain=x/L)??? And hence the resistance decrease??
When strain is applied,the length of the wire present in the box increases.We know that R is directly proportional to L,so an increase in the length increases the resistance.Increase in the resistance is inversely proportional to Cross sectional area hence the area decreases,therefore the answer is D.Hope this helps:)
 
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for the 9th.. i think we cant prove it numerically but one think is for sure that initial momentum is 2mv... and if collision were perfectly elastic ones, max. momentum change would have been 2mv-(-2mv) =4mv... now it is given that collision was inelastic, it momentum change should have been less than 4mv and greater than 2mv.. so we have only one option to satisfy this... option C...
Thank you very much. :)
 
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For Q15
initial momentum is zero cuz both trolleys are at rest.When they are released let velocity of 1 kg trolley be v
Using conservation of momentum
0=2*2-1*v which will give u v=4 m/s.Now
Energy of spring=Kinetic energy of each trolley
E=1/2*2*2^2 + 1/2*1*4^2 givin u D answer
For Q22
you have to use the formula
E=Fl/eA where E is young modulus,l is length,e is extension and A is area.First calculate area then put the values in the formula.Bring the formula in the form so that e is divided by l cuz he has asked by what percent string contracts.Dont forget to multiply it by 100.
For Q26
First find line spacing
d=10^-3 divided by 300
Now use the formula d sintheta=n lambda
Put 90 in place of theta and find n.It will be something like 7.4 i dun know.But take n as 7 dont round it to 8.Now he has asked for maximum orders so 2n+1=15
For Q28
Since drop is stationary so that means some force must be equal to its weight.Since weight is acting downwards this force must be acting upwards.The upper plate is +ve so that means the drop must be negative for it to be attracted to upper plate.If it was positive it wont have been stationary.W=mg To find charge use the formula F=qE where q=F/E Now substitute F with W since they both are equal mg=qE which will give charge to mass ratio as g/E
That was very helpful, thank you so much! I have a question, though - For Q.26, why did you do 2n+1? Is that something I'm supposed to know?
 
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