AQA physics unit 5 sig fig

I leave everything in untill the last answer e.g. if my calculator gives a long answer, I'll write that down. That way theres no way they could penalize me up untill the end when I round to 3 sig fig.

3 Quick questions :-)
1. if the answer said 3.0 x10-4 on the mark scheme and i wrote 30x-3 in my answer would i still get the mark even though its written differently on the mark scheme? How do you know which power of 10 to use?

2.when doing a question where you have to use a previous answer you've worked out do you use the rounded answer or the unrounded answer

3. When doing a question where you have to show something is equal to a certain value, do you have to use the 'show me' answer in the next part of the working or the actual worked value.

1. The rule is that if you have

y x 10^x
and
y>=10
you make y<10 and increase the x accordingly

For example

90 x 10^3 becomes 9.0 x 10^4 (because 90>=10)
55 x 10^9 becomes 5.5 x 10^10 (because 55>=10)
30 x 10^-3 becomes 3.0 x 10^-2 (because 30>=10)
100 x 10^3 becomes 1.0 x 10^5 (because 100>=10)
1000 x 10^2 becomes 1.0 x 10^5 (because 1000>=10)
10 x 10^-2 becomes 1.0 x 10^-1 (because 10>=10)
and so on

2. Its always good practice to use the unrounded answer (stops errors creeping in) but it doesn’t matter too much, as a check you can see if you get the same number with the rounded and unrounded answer.

If the previous question specified a degree of accuracy use the rounded answer.

For example

the question says 'use the answer you got in the previous question to....'

and your previous question said 'give you anwser to (e.g.) 2.s.f'

use the rounded answer.


3. same as 2. As they specified a value/number/accuracy in the 'show me' just use the show me anwser

Hope that clears it up abit :-)

Thank you so so so much!

1. The rule is that if you have

y x 10^x
and
y>=10
you make y<10 and increase the x accordingly

For example

90 x 10^3 becomes 9.0 x 10^4 (because 90>=10)
55 x 10^9 becomes 5.5 x 10^10 (because 55>=10)
30 x 10^-3 becomes 3.0 x 10^-2 (because 30>=10)
100 x 10^3 becomes 1.0 x 10^5 (because 100>=10)
1000 x 10^2 becomes 1.0 x 10^5 (because 1000>=10)
10 x 10^-2 becomes 1.0 x 10^-1 (because 10>=10)
and so on

2. Its always good practice to use the unrounded answer (stops errors creeping in) but it doesn’t matter too much, as a check you can see if you get the same number with the rounded and unrounded answer.

If the previous question specified a degree of accuracy use the rounded answer.

For example

the question says 'use the answer you got in the previous question to....'

and your previous question said 'give you anwser to (e.g.) 2.s.f'

use the rounded answer.


3. same as 2. As they specified a value/number/accuracy in the 'show me' just use the show me anwser

Hope that clears it up abit :-)

quick question about rounding though in a question they wanted the answer to 3 sig figs, it specified. I wrote 5.16x10^3 but they just wrote 5160, would i still get the mark or?

5.16*10^3=5160 and both ways of writing are to 3.s.f so you will get the mark

Is this GCSE level? If so, many people have trouble with powers at this level so majority of students will write '5160', so that’s why its written in the marksheme like that (easier for the ppl doing the marking to see if an answer is correct, but they will see yours is right).

If your ever worried about something like this in am exam just write:

=... (ur working)
=....(ur working)
= 5.16*10^3
=5160

omg no haha! its A2 i understand significant figures and how to use them I've just transferred to a different exam board from the one i did at AS so I'm not familiar with the mark scheme. I know theyre the same thing but only one of them is on the mark scheme and i'm not sure how specific aqa are with their marking.