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# OCR Mechanics 1 25th Jan watch

1. The ones I put down on the paper! We'll wait for MrM
2. I initially had the co-efficient of friction as 1.7 like others said, but thought it was impossible because it has to between 0 and 1, so I just crossed that all out and ended up coming up with the answer 0.426. I know that is wrong, I just wrote some forumlas down in the hope of getting some method marks.

I think I've gotten the 9 marker right at the end, it took quite a bit of working out. I got 9.5, but speaking to people afterwards everybody seemed to get different answers Did anybody else get 9.5?

Rest of the paper wasn't too bad though, I got 25m for that A and B one as well, whatever question that was. Just hoping Mr M will post the answers later

Anyway, hopefully Mr M will be posting the answers later
3. Hello answers just being typed up now.
4. (Original post by mrdude)
.
I and another here got 9.5, my friend too.
5. (Original post by mcp2)
I and another here got 9.5, my friend too.

(Original post by Mr M)
Hello answers just being typed up now.
Thanks a lot Mr M, you are extremely helpful for doing so. What did you think of the paper?
6. OCR (not OCR MEI) answers January 2010

All non-exact answer given to 3 s.f.

1. (i) Speed of P at ground = 18.9 m/s (2 marks)

(ii) Height = 17.3 m (2 marks)

(iii) Speed of P when 5 m above ground = 16.1 m/s (2 marks)

2. (i) Magnitude of resultant = 27.1 N (5 marks)

(ii) Angle = 37.4 degrees (3 marks)

3. (i) m = 0.096 kg (4 marks)

(ii) Change in momentum = 1.2 Ns (2 marks)

(iii) Common speed = 3.25 m/s (3 marks)

4. (i) (a) R perpendicular = 0.49 N

R parallel = 0.849 N (4 marks)

(b) Coefficient of friction = 1.73 (2 marks)

(ii) T = 4.36 N a = 1.09 m/s² (4 marks)

5. (i) t = 12.5 seconds (3 marks)

(ii) t = 26.7 s (5 marks)

(iii) Sketch graph (3 marks)

6. (i) a = 0.012t - 0.18 (2 marks)

(ii) Show k = 2 (5 marks)

(iii) x = 0.002t³ - 0.09t² + 2t

x = 30.0 m (5 marks)

7. (i) T = 1960 N (5 marks)

(ii) (a) Show 3.15 (2 marks)

(b) t = 9.50 seconds (9 marks)

Edit: question 7 fixed.
7. (Original post by mcp2)
I and another here got 9.5, my friend too.
Just checking the last one because I didn't get 9.5!
8. (Original post by Mr M)
Just checking the last one because I didn't get 9.5!
slightly worried cos I got 9 something or other too.
9. (Original post by Mr M)
Just checking the last one because I didn't get 9.5!
OK thanks, I found the distance and time travelled upwards (it still had momentum) and then the time taken to travel 10+extra distance downwards.
10. (Original post by mcp2)
OK thanks, I found the distance and time travelled upwards (it still had momentum) and then the time taken to travel 10+extra distance downwards.
Yeah that's what I did, and the on the blocks movement back down the plane I switched the direction of friction to oppose motion. I'm hoping Mr M made a mistake!
11. (Original post by mrdude)
Yeah that's what I did, and the on the blocks movement back down the plane I switched the direction of friction to oppose motion. I'm hoping Mr M made a mistake!
Ah-ha! Didn't switch direction of friction when I did it. Schoolboy error!
12. (Original post by Mr M)
Ah-ha! Didn't switch direction of friction when I did it. Schoolboy error!
pfft, idiot

Joking of course! Did you get 9.5 after your correction?
13. (Original post by Mr M)
Ah-ha! Didn't switch direction of friction when I did it. Schoolboy error!
Aha, you had me worried for a minute there as I was sure I got 9. something, what was the actual answer then?

Looking at your answers has reassured me, I'm pretty certain I did good.
14. (Original post by Mr M)
Ah-ha! Didn't switch direction of friction when I did it. Schoolboy error!
Brilliant! you had me worried for a minute then!

Fingers crossed if the 9 marks is 9.5, i have 57/72 which I would be delighted with.

I took M1 3 times in college 5 years ago and never got higher than an E grade.

Amazed that 1.73 is the correct answer. I wasted alot of time going over this question convinced that the coefficient couldnt be higher than 1!
15. COEFFICIENT OF FRICTION QUESTION:

The particle is moving up and down. The force perpenicular to the slope is therefore friction and the force parallel with the slope is R. Answer is 0.457 or something.
16. (Original post by Mr M)
Ah-ha! Didn't switch direction of friction when I did it. Schoolboy error!

what did you think of the paper Mr M
17. (Original post by owen4567)
Brilliant! you had me worried for a minute then!

Fingers crossed if the 9 marks is 9.5, i have 57/72 which I would be delighted with.

I took M1 3 times in college 5 years ago and never got higher than an E grade.

Amazed that 1.73 is the correct answer. I wasted alot of time going over this question convinced that the coefficient couldnt be higher than 1!
9.50 secs is correct. I would amend the post but it is not letting me at the moment.

It is unusual to get a coefficient of friction that high in these questions. Usually it is less than 1 (but it doesn't have to be).
18. (Original post by gma)
COEFFICIENT OF FRICTION QUESTION:

The particle is moving up and down. The force perpenicular to the slope is therefore friction and the force parallel with the slope is R. Answer is 0.457 or something.
This was some question, certainly caused alot of debate!

Why is the particle moving up and down? It was at rest on the slope and the other particle was lighter so does friction not act up the slope?

Is this a harder paper than previous years? I am sure I have seen a grade boundary of 49 for an A in previous years?
20. (Original post by gma)
COEFFICIENT OF FRICTION QUESTION:

The particle is moving up and down. The force perpenicular to the slope is therefore friction and the force parallel with the slope is R. Answer is 0.457 or something.
I think you will find that a normal contact force is perpendicular to the plane (hence the word normal in its name).

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