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# What value should I use for gravity? Watch

1. Hi,

I am doing the M1 module in my AS maths and also mechanics appears in physics. The issue I have is that I have a shorthand 'g' button on my calculator which uses the standard 9.80665 value. I find it easier to understand when I use this when solving an equation. I am slightly worried that other people will be using 9.81 which is what we're normally told to use. In the mark scheme I have never been marked down for using the standard value however it has sometimes been the case that the 'correct' answer is not the same as what is obtained through the use of the full 'g' value. In these cases, I've found the mark scheme would say 'condone *answer*'.

I was wondering if there's a guideline somewhere which says that it's more preferential to use 9.81, as it's not in the question paper anywhere except occasionally where they give you the g value they'd like you to use.

All I want to do is prevent myself from being penalised simply because I used a slightly more accurate version of a constant than the one they were expecting me to use.

2. (Original post by OutragedSoup)
Hi,

I am doing the M1 module in my AS maths and also mechanics appears in physics. The issue I have is that I have a shorthand 'g' button on my calculator which uses the standard 9.80665 value. I find it easier to understand when I use this when solving an equation. I am slightly worried that other people will be using 9.81 which is what we're normally told to use. In the mark scheme I have never been marked down for using the standard value however it has sometimes been the case that the 'correct' answer is not the same as what is obtained through the use of the full 'g' value. In these cases, I've found the mark scheme would say 'condone *answer*'.

I was wondering if there's a guideline somewhere which says that it's more preferential to use 9.81, as it's not in the question paper anywhere except occasionally where they give you the g value they'd like you to use.

All I want to do is prevent myself from being penalised simply because I used a slightly more accurate version of a constant than the one they were expecting me to use.

Which exam board?
3. (Original post by OutragedSoup)
...
Edexcel:

OCR and OCR-MEI:

4. (Original post by Zacken)
---
Okay, so found out today I am completely blind and / or didn't look in the right places
5. (Original post by OutragedSoup)
Okay, so found out today I am completely blind and / or didn't look in the right places
What I tend to do is to work in 'g' till the end of a question where I sub in the value and give a numerical answer. Not sure if that's beneficial for you, but meh. :-)
6. (Original post by OutragedSoup)
Okay, so found out today I am completely blind and / or didn't look in the right places
If you are doing Edexcel then you will lose marks if you use anything other than 9.8.

"Use of g = 9.81 should be penalised once per (complete) question."
7. (Original post by Zacken)
What I tend to do is to work in 'g' till the end of a question where I sub in the value and give a numerical answer. Not sure if that's beneficial for you, but meh. :-)
Yes that sounds perfectly logical
8. (Original post by OutragedSoup)
Yes that sounds perfectly logical
Awesome, sorry to have to be the bearer of bad news.
9. (Original post by notnek)
If you are doing Edexcel then you will lose marks if you use anything other than 9.8.

"Use of g = 9.81 should be penalised once per (complete) question."
I'm doing AQA, but it seems silly that they'll penalise something that's not technically wrong. To be honest it's slightly more correct. However as they clearly give the instruction to use 9.8 I can see why they'd want to penalise for not obeying it.
10. (Original post by notnek)
If you are doing Edexcel then you will lose marks if you use anything other than 9.8.

"Use of g = 9.81 should be penalised once per (complete) question."
Wow.. **** those guys

If the working is correct...
11. Yep, same for AQA:

12. (Original post by Architecture-er)
Wow.. **** those guys

Isn't this why we provide working in the first place
I'd much rather it be like STEP and be required to leave everything in algebraic quantities rather than numerical approximations.
13. (Original post by Architecture-er)
Wow.. **** those guys

If the working is correct...
Exams are just as much about following instructions as knowing how to do maths, fortunately or unfortunately.
14. (Original post by OutragedSoup)
I'm doing AQA, but it seems silly that they'll penalise something that's not technically wrong. To be honest it's slightly more correct. However as they clearly give the instruction to use 9.8 I can see why they'd want to penalise for not obeying it.
All of the M1 questions you do make assumptions all over the place. Taking g as 9.8 is just another one.
15. (Original post by notnek)
All of the M1 questions you do make assumptions all over the place. Taking g as 9.8 is just another one.
That's a really good point tbf

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