# [urgent]help me solve class X physics questions



## Niilesh (Mar 23, 2012)

Hey Can someone solve these question and explain it?
I want the answer before 25th(till 24th)
*i.imgur.com/E6RFX.jpg

I didn't even understand this-
*i.imgur.com/OIeAe.jpg

A maths one(this one seems impossible)

81. The area of quadrilateral ABCD whose sides are 9 m, 40 m, 28 m and 15 m is  
 (A) 300 m2
 (B) 306 m2
 (C) 296 m2
 (D) none of these

*Update:* solved the first and the third 
can someone explain the second?
at least just what it means?


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## avichandana20000 (Mar 23, 2012)

YOUR QN REFRMAED:

I have a parcel with four sides with lengths of 9 on the north, 40 on the south, 28 on the west and 15 on the east. I do not know any of the angles and presume that none of them are right angles. Also presume that none of the sides are parallel to each other.

I can't divide it into two triangles and calculate those areas using the formula 1/2 b X h because neither of the triangles would have a right angle.

How do I go about calculating the area?



use Brahmagupta Formula:

A = SqRt[(s-a)(s-b)(s-c)(s-d)]

a, b, c and d are the lengths of the four sides of the quadrilateral, and s = (a + b + c + d)/2.

s=(9+40+28+15)/2=46

Area=Sq rt(46-9)(46-40)(46-28)(46-15)

       =Sq rt(37)(6)(18)(31)

       =Sqrt(123876)

       =351.96

So Answer is D

hope this helps.


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## Niilesh (Mar 24, 2012)

^
the formula only applies to cyclic quadrilateral
Answer is B (i have answer key)
actually the question is wrong but it has a special case in it a pythagoras triplet
*i.imgur.com/WRmI0.jpg
Area of quad = 126 + 180 (by herons formula) = 306

Also i solved the first question


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## dashing.sujay (Mar 24, 2012)

^How did you solved 3rd ?


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## Niilesh (Mar 24, 2012)

^ you mean first?
I didn't solve the second one


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## dashing.sujay (Mar 24, 2012)

No 3rd.


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## Niilesh (Mar 24, 2012)

This is the fig is:
*i.imgur.com/wXkfF.jpg

Now area of quadrilateral = area of two triangles
Area of triangle with sides 40,41 and 9 is 180(1/2*40*9)
area of other triangle is 126(herons formula)
total = 306 units

PS: i didn't label the image properly before


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## dashing.sujay (Mar 24, 2012)

How can you consider the figure to be that way along with right angles?


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## Niilesh (Mar 24, 2012)

Actually the question is wrong
But i found that it had a Pythagoras triplet so just put a right angle there
BTW in the question the order is 9,40,28,15
switch the 28 and 15 sides in my fig and there you have it - the required quadrilateral 

also if you consider it to be a trapezium with height 9 and with parallel sides 40 and 28 the area is same


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## vaibhav23 (Mar 24, 2012)

^In that maths question if you do it the other way round that is 28^2+15^2 then the hypotenuse should be equal to 41 but it is not coming to 41.  
In a quardilateral if one angle is 90 all other angles should be also 90 all this leading to that it is either a rectangle or a square


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## Niilesh (Mar 24, 2012)

vaibhav23 said:


> ^In that maths question if you do it the other way round that is 28^2+15^2 then the hypotenuse should be equal to 41 but it is not coming to 41.
> In a quardilateral if one angle is 90 all other angles should be also 90 all this leading to that it is either a rectangle or a square



hey man who said that other triangle is also right angled?

"In a quardilateral if one angle is 90 all other angles should be also 90 all this leading to that it is either a rectangle or a square" - this line is wrong. Go revise the basics
PS: no offence


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## dashing.sujay (Mar 24, 2012)

Answer of second is?


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## Niilesh (Mar 24, 2012)

^(c)

char


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## vaibhav23 (Mar 24, 2012)

Niilesh said:


> hey man who said that other triangle is also right angled?
> 
> "In a quardilateral if one angle is 90 all other angles should be also 90 all this leading to that it is either a rectangle or a square" - this line is wrong. Go revise the basics
> PS: no offence


^Sorry I mixed it up a little.
BTW  what was the answer you got for the first one


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## Niilesh (Mar 24, 2012)

Its again C
you will not understand it without knowing trigno and of course snells law


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## vaibhav23 (Mar 24, 2012)

^I have studied that chapter in class 9 and have took out the answer.
My one is also C but wanted to cross check with how you got the answer


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## Niilesh (Mar 24, 2012)

^
I learned it in class X(since NCERT of class IX didn't have those topics and i was not preparing for competitive exams)

You want to know the solution?


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## Gollum (Mar 25, 2012)

I give up, OMG I hate studies *runs away screaming*


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## Niilesh (Mar 25, 2012)

^ 
BTW Test was held today
It went better than my expectation


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## dashing.sujay (Mar 25, 2012)

^Share the results too


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## Niilesh (Mar 25, 2012)

Ok ,they will come on 28th

finally i can enjoy the holidays


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## vaibhav23 (Mar 25, 2012)

Niilesh said:


> ^
> I learned it in class X(since NCERT of class IX didn't have those topics and i was not preparing for competitive exams)
> 
> You want to know the solution?


Yup
You are taking pinnacle course from which city?
If you want you can take the pinnacle course from South Delhi as it is the best fiitjee institute


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## Niilesh (Mar 26, 2012)

^
I live in Jaipur (you can see that with the post count on the left)


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## kuki_295 (Mar 26, 2012)

In second ques, magnetic force only acts on moving charged particles so it'll just sit there. 
Is there magnetism chapter is 10th class.
Explaining the question: a charged particle is on a table tied to a string and there is a magnetic field perpendicular to table surface.


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## Niilesh (Mar 26, 2012)

kuki_295 said:


> In second ques, magnetic force only acts on moving charged particles so it'll just sit there.
> Is there magnetism chapter is 10th class.
> Explaining the question: a charged particle is on a table tied to a string and there is a magnetic field perpendicular to table surface.


I didn't read that
BTW magnetism was in 9th


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## Niilesh (Mar 28, 2012)

Got 185/270
90% scholarship (highest)


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## dashing.sujay (Mar 28, 2012)

Can you share the questions ?


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## Niilesh (Mar 28, 2012)

^ The question paper was taken with the OMR sheet but if you want i can post few questions that i can remember


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## dashing.sujay (Mar 28, 2012)

Yes please.


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## Niilesh (Mar 28, 2012)

Q. What is the chemical formula of Magnesite?

Q. Bronze is made up of which metals?

Q. There are 256 pages in a book how many integers are used?(Its a little tricky to understand what he is saying)

Q.Heart:throb::Eye: ?

Q. how many polygons are there in this figure?
*i.imgur.com/xwtzG.jpg


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## dashing.sujay (Mar 29, 2012)

Can't answer first four 

Last answer 22 ?


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## Neo (Mar 29, 2012)

The questions are easy, except for the first one. I haven't read that word before  was it the fiitjee exam?

Sent from my LG-P500 using Tapatalk 2 Beta-2


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## Niilesh (Mar 29, 2012)

dashing.sujay said:


> Can't answer first four
> 
> Last answer 22 ?



22!!! how did you found this much???!!!
Options are: 
A.6
B.8
C.10
D.4



Neo said:


> The questions are easy, except for the first one. I haven't read that word before  was it the fiitjee exam?
> 
> Sent from my LG-P500 using Tapatalk 2 Beta-2



Me too!!!
ya, they are from Fiitjee entrance exam
Maths and IQ saved me in this test


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## dashing.sujay (Mar 29, 2012)

I suck


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## Neo (Mar 29, 2012)

is there any other Fiitjee exam going to be held for admission to class 10?


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## Niilesh (Mar 29, 2012)

dashing.sujay said:


> I suck


Whats your stream?
BTW I again looked at that figure and found that there are 12 polygons(during the test i counted 8!) 
But i am sure there was no option greater than 10
That means two things- either there was an option "none of these" or there was only one line in the center
If its the first case it explains one of the two wrong answers in IQ. 


Neo said:


> is there any other Fiitjee exam going to be held for admission to class 10?


There are still 7 tests to be held for admission to class XI & i mostly test for all tests are held together soo..
They will be 3 or 4 tests in April


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## AcceleratorX (May 6, 2012)

Kinda sucks, I have learnt not to put much thought or effort into this kind of test. It's easy to solve for those who are trained to do it. Not so much for others, which invalidates the rule of equal opportunity 

Heck, I find quantum physics making more sense than some of this stuff


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## dashing.sujay (May 6, 2012)

Niilesh said:


> Whats your stream?



PCM. I know the mistake I did (def of polygon )


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## kuki_295 (May 6, 2012)

well polygon can be of any shape Polygon - Wikipedia, the free encyclopedia
if the question asks about regular polygons(all equal angle) then i was able to find.
4 small square
1 bigger square
1 biggest square

other polygons 
8 triangles
2 hexagon
4 pentagon of one kind
4 pentagon of other kind
8 trapeziums 
4 rectangles
even more possible i think.


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