ccchimpo
Badges: 7
Rep:
?
#1
Report Thread starter 1 month ago
#1
Can someone help with this question.

Says A is on the point of moving down the plane and is on a rough plane.
So shouldn't horizontal motion be greater than tension and friction? So the equation of motion be:
mgsin30 - F - T = ma ?? (where F is friction and mgsin30 is resolving parallel to the plane)
The mark scheme's equations:
T + F - mgsin30 = ma (for part (a)(ii))
T - F - mgsin30 = ma (for part (b))
But that would mean tension > horizontal motion, meaning A is moving up the plane??
0
reply
ccchimpo
Badges: 7
Rep:
?
#2
Report Thread starter 1 month ago
#2
Here's the question with diagram:Name:  Q5.png
Views: 18
Size:  121.3 KB

Can someone honestly just explain the whole question to me cause mechanics is gonna be the death of me fr.
0
reply
laurawatt
Badges: 21
Rep:
?
#3
Report 1 month ago
#3
Have you drawn the force diagram and labelled everything?

The system is on the point of moving (limiting equilibrium) so the forces pulling up and the forces pulling down exactly equal each other

In part aii and part b, the value of lambda and mu are different, that’s why you get different equations
0
reply
ccchimpo
Badges: 7
Rep:
?
#4
Report Thread starter 1 month ago
#4
(Original post by laurawatt)
Have you drawn the force diagram and labelled everything?

The system is on the point of moving (limiting equilibrium) so the forces pulling up and the forces pulling down exactly equal each other

In part aii and part b, the value of lambda and mu are different, that’s why you get different equations
Ohh ok so for part (a) forces up equal forces down.
For part (b) though, because it is now accelerating, I thought the equation for particle A would be mgsin30 - T - F = 1/4 mg , but the mark scheme says T - F - mgsin30 = 1/4 mg.
Particle A is moving down the slope so shouldn't horizontal force be greater than tension + friction ?
0
reply
ccchimpo
Badges: 7
Rep:
?
#5
Report Thread starter 1 month ago
#5
Oh wait nvm. My error was linking part (a) to part (b), when they are independent of each other. If lambda is 2 then the mass of B is greater than that of A so rather than A moving down the slope, it is now moving up the slope.
1
reply
nitron10
Badges: 1
Rep:
?
#6
Report 1 month ago
#6
(Original post by laurawatt)
Have you drawn the force diagram and labelled everything?

The system is on the point of moving (limiting equilibrium) so the forces pulling up and the forces pulling down exactly equal each other

In part aii and part b, the value of lambda and mu are different, that’s why you get different equations
i worked it all out, got the first answer right but cannot do question b
0
reply
lara147
Badges: 15
Rep:
?
#7
Report 1 month ago
#7
(Original post by ccchimpo)
Here's the question with diagram:Name:  Q5.png
Views: 18
Size:  121.3 KB

Can someone honestly just explain the whole question to me cause mechanics is gonna be the death of me fr.
Do you know what the answers are?
0
reply
lara147
Badges: 15
Rep:
?
#8
Report 1 month ago
#8
(Original post by nitron10)
i worked it all out, got the first answer right but cannot do question b
Where can I find the answers? I worked it out but I cant seem to find the answers online
0
reply
username5340678
Badges: 6
Rep:
?
#9
Report 1 month ago
#9
(Original post by ccchimpo)
Here's the question with diagram:Name:  Q5.png
Views: 18
Size:  121.3 KB

Can someone honestly just explain the whole question to me cause mechanics is gonna be the death of me fr.
That’s definitely MEI! Did you go and see the additional assessments 2021, I believe they have the same type of questions on this.
+ this doesn’t look like a 2020 mechanics (I’ve done this paper before in my school) I’m thinking it’s a 2019 P1
0
reply
ccchimpo
Badges: 7
Rep:
?
#10
Report Thread starter 1 month ago
#10
(Original post by lara147)
Where can I find the answers? I worked it out but I cant seem to find the answers online
It’s ocr alevel maths pure & mechanics 2018 paper. The mark scheme is on the ocr website
0
reply
ccchimpo
Badges: 7
Rep:
?
#11
Report Thread starter 1 month ago
#11
Mark SchemeImage:
https://www.ocr.org.uk/Images/535623...-mechanics.pdf

It is Q12
0
reply
lara147
Badges: 15
Rep:
?
#12
Report 1 month ago
#12
(Original post by ccchimpo)
It’s ocr alevel maths pure & mechanics 2018 paper. The mark scheme is on the ocr website
Oh okay thanks I got both answers right do you still want to see the working out I did?
0
reply
ccchimpo
Badges: 7
Rep:
?
#13
Report Thread starter 1 month ago
#13
(Original post by lara147)
Oh okay thanks I got both answers right do you still want to see the working out I did?
Yes please, that’d be awesome!
1
reply
lara147
Badges: 15
Rep:
?
#14
Report 1 month ago
#14
(Original post by ccchimpo)
Yes please, that’d be awesome!
Name:  A6FC01B4-0B89-4C91-8C5D-F4B1FBE4E6CB.jpg.jpeg
Views: 17
Size:  29.1 KBName:  0448FCF5-E3F2-41D7-AD76-73A3495FD7CC.jpg.jpeg
Views: 7
Size:  25.5 KB
0
reply
ccchimpo
Badges: 7
Rep:
?
#15
Report Thread starter 1 month ago
#15
(Original post by lara147)
Name:  A6FC01B4-0B89-4C91-8C5D-F4B1FBE4E6CB.jpg.jpeg
Views: 17
Size:  29.1 KBName:  0448FCF5-E3F2-41D7-AD76-73A3495FD7CC.jpg.jpeg
Views: 7
Size:  25.5 KB
Thank you so much that helped so much!
0
reply
X

Quick Reply

Attached files
Write a reply...
Reply
new posts
Back
to top
Latest
My Feed

See more of what you like on
The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

Personalise

Do you think receiving Teacher Assessed Grades will impact your future?

I'm worried it will negatively impact me getting into university/college (221)
43.42%
I'm worried that I'm not academically prepared for the next stage in my educational journey (58)
11.39%
I'm worried it will impact my future career (39)
7.66%
I'm worried that my grades will be seen as 'lesser' because I didn't take exams (107)
21.02%
I don't think that receiving these grades will impact my future (56)
11%
I think that receiving these grades will affect me in another way (let us know in the discussion!) (28)
5.5%

Watched Threads

View All
Latest
My Feed

See more of what you like on
The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

Personalise