Time to redeem yourselves (maffs)

Originally Posted by the_lone_wolf

yes, but when you accelerate you cover distance at an ever increasing rate

although the rate of acceleration is doubled if you double the force, if you are only allowed to accelerate for a set distance, twice the force will not equate to twice the final speed, because the time it takes to cover that set distance decreases exponentially when you accelerate more quickly

Erm. Not quite. Remember the KISS theory?

The force is only applied to get the ball moving. Therefore, once it's started moving, there is no force, therefore no acceleration.

Also, see my previous post, I edited it as just "F=ma" was a tad naughty of me.

EDIT: Keithd, I have a significant other, and 3 kids... Go figure.

Originally Posted by Baph

EDIT: Keithd, I have a significant other, and 3 kids... Go figure.

you married your maths teacher?!

only joshin' i'm sure you know that!! how i got "o" level maths is beyond me...and i used to be awesome at solving all them x2 + y 2 dollars an hour equations things! ....

Originally Posted by keithd

only joshin'

No, really?

Glazed over at the first question....complete gobbledygook to me - I just dont get this sort of maths - or even understood the reasons for it?!!! I got ungraded in my maths CSE

I'll stick with my Arts degree!

uh oh, back to school for me, I think Primary school would be best!!!

[the_lone_wolf]

Originally Posted by Baph

But that's far too complex. I've been working with KISS for a long long time. I saw the question & insinctively knew the answer. I guess my brain is wired up different to yours TLW.

i knew what they wanted me to answer, but the question wasn't worded correctly in order to convey the meaning they intended...

what they meant to say was that if a ball is rolled at twice the speed, the way in which the ball reached the speed is irrelevant, but to say that a force is used to roll the ball is inaccurate, because it implies that an acceleration occurs.

if, as your post says, they meant that twice the force is used to accelerate the ball from rest until it reaches the speed at which we begin to time it's passage from one point to the other then they have not given you enough information in order to determine the speed of the ball at t=0

double the force would not necessarily mean double the starting speed, as i showed previously, as it depends on how long the force is applied to the ball

KISS is a great acronym, but KIASAP is better, keep it as simple as possible - you wouldn't say to someone who you commission to build you a car "make me something with wheels and an engine" - you would have to specify details otherwise you wouldn't get what you want. in the same way, if you don't give enough details or use the wrong terminology when asking a question such as the one on the quiz you leave yourself open to misinterpretation.

three years studying physics at university drums into you the importance of using correct terminology, units etc, as without it the question is meaningless - mistaking a speed for a force is elementary stuff, you would most definitely be expected to know the difference when you walked in the door

So far, 17/20, but I'm stuck on the stratified sample one. I haven't heard of that before.

Edit: got that one right, now stuck on q.19. This is much harder than the English one.

Edit2: Whoo, 20 out of 20. I did have to read up on how to solve the factorising one.

Originally Posted by wyrdness

So far, 17/20, but I'm stuck on the stratified sample one. I haven't heard of that before.

Edit: got that one right, now stuck on q.19. This is much harder than the English one.

It is quite a simple of, you basically multiply out the terms out of the first bracket by what is the in the second bracket. Let's take the factors of answer 1:

Take this:
(x + 1) (x -1)

Expand out the multiplication:
(x * (x -1)) + (1 * (x - 1))

Do the multiplication inside the brackets:
(x^2 - x) + (x - 1)

Take the brackets out:
x^2 - x + x - 1

Do the maths and you get this:
x^2 - 1

So answer no 1 isn't it.

However since this is multiple choice you can cheat and not do the expansion for all 4 equations based on one of the terms in the answer. I think you can see the answer now.