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# M1 Moments watch

1. (Original post by Zacken)
I don't think so (did it in my head so you might very well be right), no, did you get ?
on my sheet i wrote R=3g+4g+1g=13g addition skills competent
2. (Original post by thefatone)
i got the distance as 6/13 metres is that right?
No
3. (Original post by thefatone)
on my sheet i wrote R=3g+4g+1g=13g addition skills competent
xD Your method is fine, then. Just a silly arithmetic slip.
4. (Original post by Student403)
No
3/3
5. (Original post by Zacken)
3/3
6. (Original post by Zacken)
xD Your method is fine, then. Just a silly arithmetic slip.
that cost me 3 marks in a C2 paper we did in class, i though that when i was solving for y one of the brackets was (13-10)² i got that as 2² >.>
that was 2 marks and the other question i just didn't write the answer >.> cost me 1 mark, overall i got 71/75 which i thought wan't bad, i guess i can post the things on here(note: we did the paper in 2 separate lesson so the order of me doing the questions is a bit weird)
7. (Original post by Zacken)
Nah, you got the first post.

Edit: wait for TeeEm's comment.
am I too late ?
I was out for my daily walk ...
8. (Original post by TeeEm)
am I too late ?
I was out for my daily walk ...
Nopes, just on time!
9. (Original post by TeeEm)
am I too late ?
I was out for my daily walk ...
you can help me this time xD

Explain briefly the significance of modelling the parcel as a particle.

is one that air resistance is a factor?
10. (Original post by thefatone)
you can help me this time xD

Explain briefly the significance of modelling the parcel as a particle.

is one that air resistance is a factor?
No air resistance
modelling as a particle allows you to say the distance of the parcel from a a given point is exactly (....) metres
11. (Original post by TeeEm)
No air resistance
modelling as a particle allows you to say the distance of the parcel from a a given point is exactly (....) metres
ok thanks also if the question says non-uniform plank do i put the mass of the plank right at the centre of it?
12. (Original post by thefatone)
you can help me this time xD

Explain briefly the significance of modelling the parcel as a particle.

is one that air resistance is a factor?
A nice page from Edexcel's textbook just to quickly read over. Don't think you need to memorize all this

Not sure if your exam board has all these terms too

13. (Original post by Student403)
A nice page from Edexcel's textbook just to quickly read over. Don't think you need to memorize all this

Not sure if your exam board has all these terms too

oh ok thanks
14. (Original post by thefatone)
ok thanks also if the question says non-uniform plank do i put the mass of the plank right at the centre of it?
No, that's what "non-uniform" means, that the mass isn't at the centre, you'll need to label the distance of the centre of mass from one end as 'x' and find it.
15. (Original post by Zacken)
No, that's what "non-uniform" means, that the mass isn't at the centre, you'll need to label the distance of the centre of mass from one end as 'x' and find it.
okay in that case could you help draw this diagram for me then? i can't seem to get it right.

A non-uniform plank AB has length 5d and mass 8m. It's in equilibrium in a horizontal position resting on supports at the points P and Q where AP=2d and AQ=4d. A parcel of mass 6m is placed on the plank at B. The plank is on the point of tilting about Q. By modelling the plank as a rod and the parcel as a particle, calculate the distance of the centre of mass of the plank from A.
16. (Original post by thefatone)
okay in that case could you help draw this diagram for me then? i can't seem to get it right.

A non-uniform plank AB has length 5d and mass 8m. It's in equilibrium in a horizontal position resting on supports at the points P and Q where AP=2d and AQ=4d. A parcel of mass 6m is placed on the plank at B. The plank is on the point of tilting about Q. By modelling the plank as a rod and the parcel as a particle, calculate the distance of the centre of mass of the plank from A.

Think about what it means for something to be tilting about Q. What does that imply about the reaction force at P?
17. (Original post by Zacken)

Think about what it means for something to be tilting about Q. What does that imply about the reaction force at P?
thanks a bunch

itt just means that reaction force at P=0
18. (Original post by thefatone)
thanks a bunch

itt just means that reaction force at P=0
Yes, that's correct. So you should be able to find fairly easily by resolving vertically.
19. (Original post by Zacken)
Yes, that's correct. So you should be able to find fairly easily by resolving vertically.
so when Rp=0 does that mean that when i take moments about A i ignore Rp since it's 0 and use 8mgx+30mgd=14mg
20. (Original post by thefatone)
so when Rp=0 does that mean that when i take moments about A i ignore Rp since it's 0 and use 8mgx+30mgd=14mg
Yes, but it's not =14mg, you forgot to multiply by the distance of Q from A.

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