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# Edexcel M3 SHM watch

1. Ex3D Q7, Is the book wrong?

Q9 part B, max EPE = max KE, how do I find max EPE?
12/2.4(0.2^2+1.4^2) = 10 is wrong.
2. Zacken, wrong forum
3. iEthan pls.

(Original post by AlmostNotable)
Ex3D Q7, Is the book wrong?

Q9 part B, max EPE = max KE, how do I find max EPE?
12/2.4(0.2^2+1.4^2) = 10 is wrong.
Please post a picture of the question?
4. (Original post by AlmostNotable)
Ex3D Q7, Is the book wrong?

Q9 part B, max EPE = max KE, how do I find max EPE?
12/2.4(0.2^2+1.4^2) = 10 is wrong.
I would use rather than energy considerations.
5. (Original post by aymanzayedmannan)
Zacken, wrong forum
Ops
6. (Original post by aymanzayedmannan)
I would use rather than energy considerations.
Should work both ways right?
7. (Original post by Zacken)
iEthan pls.

Please post a picture of the question?
http://www.physicsandmathstutor.com/...-solutionbank/
CH3 -> EX3D
8. Just use surely?
9. (Original post by AlmostNotable)
Should work both ways right?
Yes, using energy considerations worked for me - got an answer of 2.56 J both ways. I'm talking about Q7. I'll take a look at 9 as well. Are you using and converting everything to m?

EDIT: 9(b) works the same way
10. (Original post by Zacken)
Just use surely?
Q7A or Q9B?
11. (Original post by aymanzayedmannan)
Yes, using energy considerations worked for me - got an answer of 2.56 J both ways. I'm talking about Q7. I'll take a look at 9 as well. Are you using and converting everything to m?

EDIT: 9(b) works the same way
9B-What did you have for max EPE?
12. (Original post by AlmostNotable)
Q7A or Q9B?
Both.
13. (Original post by Zacken)
Both.
Maybe I didn't explain it well.
I have used v=wa and I did get the right answer.
For Q9B, what values did you use for max EPE?
14. (Original post by AlmostNotable)
..
For Q7: max E.P.E:
15. (Original post by AlmostNotable)
Q7A or Q9B?
Works for both

(Original post by AlmostNotable)
9B-What did you have for max EPE?
I used . Multiplied by 2 because there's stretching in both strings
16. Moved to Maths.
17. (Original post by AlmostNotable)
Maybe I didn't explain it well.
I have used v=wa and I did get the right answer.
For Q9B, what values did you use for max EPE?
For 9B:
18. (Original post by Zacken)
For 9B:
(12/2.4)(1.4^2-0.2^2) is what I used. No way of finding max EPE by subtracting EPE of the individual springs?
19. (Original post by AlmostNotable)
(12/2.4)(1.4^2-0.2^2) is what I used. No way of finding max EPE by subtracting EPE of the individual springs?
No, you'd need to add E.P.E of each string, it's not a vector quantity so them acting in opposite directions doesn't mean you subtract them. It's like subtracting two E_k's of a particle when you want to find the total E_k, it's not correct, you need to add.
20. (Original post by Zacken)
No, you'd need to add E.P.E of each string, it's not a vector quantity so them acting in opposite directions doesn't mean you subtract them. It's like subtracting two E_k's of a particle when you want to find the total E_k, it's not correct, you need to add.
1.4^2+0.2^2 gives me a worse answer. Have to use 0.6^2 then?

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