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Posted
It's all about remembering the difference of two squares, it also becomes useful for imaginary numbers (getting i's to the top) and simplifying nasty functions of cos, sin, cosh and sinh.

And you can use sum of two squares as well with imaginary numbers.

 

eg. x² + y² = (x + yi)(x - yi)

 

Not that it's as useful...

  • 3 weeks later...
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Posted

Last GCSE tommorow - Physics Seperate Science. I'm looking at a past paper and cannot for the life of me figure out this question:

 

The mass of the satellite is 1000kg. Calculate its weight in this orbit.

 

Any ideas?

 

edit: Oh, its a geostationary satellite so it takes 24 hours to fully orbit the globe.

Posted

I'm such a retard. I was reading the wrong question :blank:. Sorry, my desk is covered in sheets.

 

The question was - "The geostationary orbit is at a radius of 424000 km. Calculate the centripetal acceleration for this orbit".

Posted
I'm such a retard. I was reading the wrong question :blank:. Sorry, my desk is covered in sheets.

 

The question was - "The geostationary orbit is at a radius of 424000 km. Calculate the centripetal acceleration for this orbit".

 

Thats a GCSE question?!?

 

Shit, I'm going to do badly tommorrow...

Posted

Anybody fancy describing how CCD's work to me in laymans terms? Wikipedia has left me baffled.

 

Also, are devices with 3CCD's analogue? :s

Posted
Also, are devices with 3CCD's analogue? :s

 

No I think anything with a CCD is digital.

 

Most devices have three CCDs. A CCD is a light sensor. Visible light consists of red, blue and green. Therefore there are 3 CCDs, one for each colour.

I'm not sure how to explain it properly but I'll try:

Let's take a LCD monitor for instance. It has a set amount of pixels, for instance mine is 1280*1024 which is about 1.3 Megapixels (you surely are familiar with this term in digital cameras). Now each of these pixels has three transistors (red, green, blue) so that the pixel can take any colour.

The CCD is basically the same but the other way round, it doesn't emit light but rather absorbs it - as previouly said it's a sensor.

And to be able to store a colour picture on your digital camera you need three of those. One for each colour.

If you have photoshop open a colour picture and then go to the channels tab (normally next to the layers) and de- and reactivate some of the channels, that should give you a good idea how this works.

 

Hope that helped.

  • 2 months later...
Posted

If anyone can answer this before 12:05, they get a prize.

 

Using 8 bit two's compliment, how would I represent the binary number -120?

When I get an answer, it is always 00000000 : /

Posted

1111000

 

(I think.) The cheaters way to do it is to load up Window's calculator, put it in scientific mode, type in your number then change the mode to binary.

 

Edit: Actually maybe there should be a leading one too:

11111000

 

I dunno ...

 

Edit2: Changed my mind again (just noticed it was -120):

 

10001000

Posted
1111000

 

(I think.) The cheaters way to do it is to load up Window's calculator, put it in scientific mode, type in your number then change the mode to binary.

 

Theres only 7 characters there :s

 

But yes, I know you can use a calculater, but it only gives you the signed bit answer afaik

Posted

I think my Edit2 is right.

 

As it's negative there is a leading one. The remaining seven digits of the represent 8 as -128+8=-120, as required.

 

Never come across this stuff before. Wikipedia to the rescue.

Posted

If there are only 7 characters add an extra 0 on at the beginning of the number.

 

01111000

 

Two's compliment is a bitch. from what I remember of Higher Computing. Get the number into normal binary, then switch the 1s to 0s and vice-versa, then add a 1.

Posted
I was wondering when this thread would be revived. I have a purpose on the boards again :P

You and me both. I was going to bump it for the new school year. (has that started yet?)

Posted
If there are only 7 characters add an extra 0 on at the beginning of the number.

 

01111000

 

Two's compliment is a bitch. from what I remember of Higher Computing. Get the number into normal binary, then switch the 1s to 0s and vice-versa, then add a 1.

 

Thats the theroy, but whenever I try, I always end up with 00000000 : /

 

thanks odwin :D

Posted

I need to come up with a treatment and synopsis for a 4 minute factual documentary dealing with issues affecting modern Glasgow for a Ch 4 short slot.

 

I'm away to a festival tomorrow morning so if you can have it done by Monday and PM me it that'll be great.

 

Also no pressure...but if it's no good then I'm not accepted into Second year. good luck candidates.....

 

 

 

Joking! But still I should get started :P

Posted

holy cow, that's great help, chris. i'm serious. i wikied already on just "elvis" but the biographical material wasn't what i needed. thanks a lot. guess i have much to learn about wiki. :)

  • 2 weeks later...
Posted

Revived

 

Anyway. I need help with some evil surds and i know there are some very good maths people.

 

Simplify:

 

(Root 2 - 1 ) (Root 2 + 1)

 

I got Root 2 + 1, but knowing me i'll be wrong. So any help would be great please :)

Posted
Revived

 

Anyway. I need help with some evil surds and i know there are some very good maths people.

 

Simplify:

 

(Root 2 - 1 ) (Root 2 + 1)

 

I got Root 2 + 1, but knowing me i'll be wrong. So any help would be great please :)

 

I got the answer as 1.. root 2 x root 2=2

then root 2 x +1= +root 2

then root 2 x -1 = -root 2 meaning the root 2 cancel out.

then +1 x-1=-1 therefore 2-1=1 :D

 

1! but I'm probably wrong :)

Posted
Revived

 

Anyway. I need help with some evil surds and i know there are some very good maths people.

 

Simplify:

 

(Root 2 - 1 ) (Root 2 + 1)

 

I got Root 2 + 1, but knowing me i'll be wrong. So any help would be great please :)

 

(Root 2 - 1 ) (Root 2 + 1) gives you 2 - Root 2 + Root 2 -1, which equals 1.

 

Explanation:

Root 2 x Root 2 = 2

Root 2 x -1 = - Root 2

Root 2 x 1 = Root 2

1 x -1 = -1

 

 

Put simply, the answer is 1. :smile:


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