Mathematics: Post your doubts here!

[ZainH]

Pretty simple question from mechanics.
A lift bringing miners to the surface of a mine shaft is moving with an acceleration of 1.2 m.s-2 . The total mass of the cage and the miners is 1600kg. Find the tension in the cable.

For some reason I'm getting 17920, where as the answer is 17900. Ugh, help please .___.

 

[~`Heba`~ :)]

Mechanics question!
A car of mass 1000 kg moves along a horizontal straight road with its engine working at a contant rate of 25 KW. Assuming the work done by the car's engine is equal to kinetic energy generated, find the time taken to reach a speed of 30m/s.
The actual time taken is 31.6s and the car travels a distance of 680m in this time. Assuming there's an air resistance of magnitude R newtons,
(I) find the value of R.
(ii) the acceleration of the car when it's speed reaches 30m/s.
Please help thanks

 

[~`Heba`~ :)]

Pretty simple question from mechanics.
A lift bringing miners to the surface of a mine shaft is moving with an acceleration of 1.2 m.s-2 . The total mass of the cage and the miners is 1600kg. Find the tension in the cable.

For some reason I'm getting 17920, where as the answer is 17900. Ugh, help please .___.

I got 17920 too :/ , maybe the answer is corrected to the nearest 100th

 

[ZainH]

I got 17920 too :/ , maybe the answer is corrected to the nearest 100th

Sounds about right, or the book could always be wrong.
Thanks for your help x)

 

[ayeshaK]

hi can anyone here tell me any good books for pure mathematics except for the cambridge one because its not that good

 

[Prakhar]

Mj 2007. Paper 01..
Question 3.. Prove the identity
...
Help plzz

https://docs.google.com/file/d/0B87Nhbh_eflXbEZIT2lDcFF3anM/edit
i hope this will help..if u still face problems feel free to ask...

 

[Prakhar]

hello i need help with this question !! so annoying..

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Mathematics (9709)/9709_w06_qp_3.pdf

question 7(ii)..how do we solve 2 equations with 3 unknowns Oo if we have these 2 equations a+2b+c = 0 and a-2b+c = 0

pleeaasee do help me !

Sorry i can't help with P3 questions because i have completed my P1 and S1 in O/N 2012...
and i am still studying P3 and M1

maybe other users will help...

 

[Avalongria]

I can't find May/June 2002 math paper 2 cie marking scheme...PLEASE HELP

 

[yuliana95]

Pretty simple question from mechanics.
A lift bringing miners to the surface of a mine shaft is moving with an acceleration of 1.2 m.s-2 . The total mass of the cage and the miners is 1600kg. Find the tension in the cable.

For some reason I'm getting 17920, where as the answer is 17900. Ugh, help please .___.

I think your answer is correct, its just they make it into 3 significant figures.. hope it helps..

 

[iKhaled]

hello i need help with this question !! so annoying..
http://papers.xtremepapers.com/CIE/...AS Level/Mathematics (9709)/9709_w06_qp_3.pdf
question 7(ii)..how do we solve 2 equations with 3 unknowns Oo if we have these 2 equations a+2b+c = 0 and a-2b+c = 0
pleeaasee do help me !

 

[snowbrood]

i dont know how my friend solved this question the solution is below that question can anyone tell me as to how he got that angle 97.1 degrees

 

[darknessinme]

hello i need help with this question !! so annoying..
http://papers.xtremepapers.com/CIE/...AS Level/Mathematics (9709)/9709_w06_qp_3.pdf
question 7(ii)..how do we solve 2 equations with 3 unknowns Oo if we have these 2 equations a+2b+c = 0 and a-2b+c = 0
pleeaasee do help me !

You can't solve such an equation.

If you use the vector product method, you can calculate the normal of the second plane because it's perpendicular to both the direction vector of line l and normal of plane 1. It's easier to visualise this if you draw it onto paper.

 

[snowbrood]

Mechanics question!
A car of mass 1000 kg moves along a horizontal straight road with its engine working at a contant rate of 25 KW. Assuming the work done by the car's engine is equal to kinetic energy generated, find the time taken to reach a speed of 30m/s.
The actual time taken is 31.6s and the car travels a distance of 680m in this time. Assuming there's an air resistance of magnitude R newtons,
(I) find the value of R.
(ii) the acceleration of the car when it's speed reaches 30m/s.
Please help thanks

can u please tell me the source of this question so that i could read from that source and compare the answers actually i get a different value for time taken

 

[SalmanPakRocks]

Mj 2007. Paper 01..
Question 3.. Prove the identity
...
Help plzz

1-tan^2x/1+tan^2x

1-sin^2x/cos^2x * 1/1+sin^2x/cos^2x
LCM
cos^2x-sin^2x/cos^2x * 1 * cos^2x/cos^2x + sin^2x

cos^2x - sin^2x/cos^2x + sin^2x

cos^2x - sin^2x/1

1-sin^2x- sin^2x
1-2sin^2x

 

[*MK*skydiver :D]

How can I solve this ?

z^5 -6z^3 +17z -10=0

Its answer probably contains a complex number ( Pure 3 -Complex numbers chapter )


And another question please ,
Z^4 + 16 =0


==> (z^2-4i )(z^2+4i)
==> (z^2+4i)(z-2root i ) (z+2root i )
==>z=+/-( 2root i ) or z=root(-4i) <<<<what can I do to this now ?

 

[unseen95]

how to integrate 1/(2x-1)ᶺ2

 

[Binyamine]

how to integrate 1/(2x-1)ᶺ2

Let y = 1/(2x-1)ᶺ2

it can be re written as y = (2x-1)ᶺ (-2)

Differentiating gives us = -2 * [(2x-1)ᶺ (-3)] * 2
= -4 [(2x-1)ᶺ (-3)]
= -4/[(2x-1)ᶺ3]

The way of doing it, is we are differentiating the function of a function which is of the form y = [ f(x) ] ^ n

we send the power down, we subtract 1 from the power and the we multiply by the derivative of the inside of the bracket i.e by the derivative of f(x)

 

[aleezay]

Firstly, I apologise for the late reply. :/ You may not need this anymore, but this question is really interesting!

Lets say E is the expected time of reaching safety.
=> E = (1/3).2 + (1/3).(3+E) + (1/3).(5+E) (probability of 1st pick + probability of 2nd pick + probability of 3rd pick. E is added in 2nd and 3rd pick cuz the person is in the exact same scenario after travelling those 3 and 5 hours, respectively.)
=> E = [2+ (3+ E) + (5 + E)]/3
=> 3E = 2E + 10
=> E = 10.

So, it would take the person 10 hours (estimated).

Thank you for your help
We did it this way, and we THINK we got it correct (since we came second)
Let the 3 doors be A ( leading to safety in 2hrs)
B ( bringing man back in 3hrs) n
C ( " " " 5hrs)

possible pathway - probability - time taken
1. A - (1/3) - 2hrs
2. B,A - (1/3).(1/3)= 1/9 - 5hrs
3. C,A - 1/9 - 7hrs
4. B,C,A or C,B,A - 1/27 - 10hrs


so expected time= one with max probability= 2hrs

What do you think?

 

[abcde]

Thank you for your help
We did it this way, and we THINK we got it correct (since we came second)
Let the 3 doors be A ( leading to safety in 2hrs)
B ( bringing man back in 3hrs) n
C ( " " " 5hrs)

possible pathway - probability - time taken
1. A - (1/3) - 2hrs
2. B,A - (1/3).(1/3)= 1/9 - 5hrs
3. C,A - 1/9 - 7hrs
4. B,C,A or C,B,A - 1/27 - 10hrs


so expected time= one with max probability= 2hrs

What do you think?

I still think the expected time owuld be the sum of all probabilities like it always is. Your solution would be completely correct only if the maximum probabilty was 1 i.e. A was certain to happen so the expected time would definitely be 2 hours.
P.S. Which contest was this?

 

[unseen95]

Let y = 1/(2x-1)ᶺ2

it can be re written as y = (2x-1)ᶺ (-2)

Differentiating gives us = -2 * [(2x-1)ᶺ (-3)] * 2
= -4 [(2x-1)ᶺ (-3)]
= -4/[(2x-1)ᶺ3]

The way of doing it, is we are differentiating the function of a function which is of the form y = [ f(x) ] ^ n

we send the power down, we subtract 1 from the power and the we multiply by the derivative of the inside of the bracket i.e by the derivative of f(x)

hey i meant to integrate not differentiate.