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OCR (non mei) M2 Wednesday 18th May 2016

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http://www.ocr.org.uk/Images/144604-question-paper-unit-4729-01-mechanics-2.pdf
January 2013 question 8.

When I resolve I don't get the R and F force in same direction for vertical, opposite to mg. I thought the friction would be acting in the downwards incline, not up. Anyone care to explain?
Reply 41
Avatar for Sahil_
Sahil_
8
Original post by Mathematicus65
Does anyone know how to do part iii) a) and b) ...image.jpg


So we know that during a bounce whatever velocity the ball leaves the floor with will be the same as it hits the floor again. So the velocity the ball hits the ground just before second bounce is 7.84e, so the velocity of the ball after second bounce will be 7.84e^2 upwards. So using v+u+at, we can find time as -7.84e^2 = 7.84e^2 - 9.8t and rearrange to find t = 1.6e^2. Using the same principle for the time between 3rd and 4th bounce gets you t = 1.6e^3.
Reply 42
Avatar for Sahil_
Sahil_
8
Original post by Sonnyjimisgod
http://www.ocr.org.uk/Images/144604-question-paper-unit-4729-01-mechanics-2.pdf
January 2013 question 8.

When I resolve I don't get the R and F force in same direction for vertical, opposite to mg. I thought the friction would be acting in the downwards incline, not up. Anyone care to explain?

For this question, you are given that the speed of the particle is the smallest possible without slipping, meaning if it was any slower it would slip downwards towards V, therefore friction must oppose this and act upwards and parallel to plane. If the particle was travelling at its max speed then it would slip outwards if the speed increased further, meaning friction will be downwards towards V when particle is at max speed.
swahili that you??
Original post by Sahil_
For this question, you are given that the speed of the particle is the smallest possible without slipping, meaning if it was any slower it would slip downwards towards V, therefore friction must oppose this and act upwards and parallel to plane. If the particle was travelling at its max speed then it would slip outwards if the speed increased further, meaning friction will be downwards towards V when particle is at max speed.


Thank you, that its exactly what I wanted to know.
I just did Friction in both directions, and realised it must be acting upwards lol
Q7 June 2016, why doesn't the small object S have a reaction force?
Original post by Acrampage
Q7 June 2016, why doesn't the small object S have a reaction force?


June 2016? :tongue:
Original post by tinkerbella~
June 2016? :tongue:


Oops, clearly meant to say 2015 thanks :colondollar:
Reply 48
Avatar for Zacken
Zacken
22
Original post by Acrampage
Q7 June 2015, why doesn't the small object S have a reaction force?


There is a reaction force, it's just of no importance to us whatsoever because it's the rod exerting a force (and hence doesn't affect equilibria) and not the rod being exerted by a force (that bit is taken care of by the weight).
Whilst I have found Marcella to be a disappointing series so far I'm still mildly annoyed that I'm not going to let myself watch it because of M2 tomorrow :'(Good luck guys, last minute revision :wink:
Original post by rich1334
Whilst I have found Marcella to be a disappointing series so far I'm still mildly annoyed that I'm not going to let myself watch it because of M2 tomorrow :'(Good luck guys, last minute revision :wink:


My Netflix is just showing a black screen at the moment, I think it's an attempt to make me do papers instead of watching Gossip Girl :frown:
Anyone had a go at the Jan 2012 paper it's pretty hard 😕
Everyone buzzing for tomorrow?


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Original post by Zacken
There is a reaction force, it's just of no importance to us whatsoever because it's the rod exerting a force (and hence doesn't affect equilibria) and not the rod being exerted by a force (that bit is taken care of by the weight).


Thank you very much, this helped
Reply 54
Avatar for Zacken
Zacken
22
Original post by Acrampage
Thank you very much, this helped


No problem.
Original post by drandy76
Everyone buzzing for tomorrow?


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Dreading it actually :s-smilie:
Original post by Vanilla Poison
Dreading it actually :s-smilie:


If it helps I made a playlist full of my favourite chill songs to play before I go into the exam, might take a walk too


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Original post by drandy76
If it helps I made a playlist full of my favourite chill songs to play before I go into the exam, might take a walk too


Posted from TSR Mobile

Good idea, hopefully taking a walk will calm my nerves! :h:
Could someone please show me their worked solution for all of q7 part ii June 2011. I have my teachers and I just don't understand it.
Original post by Acrampage
Could someone please show me their worked solution for all of q7 part ii June 2011. I have my teachers and I just don't understand it.


Sorry this isn't a great diagram:redface:
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image.jpg248.0KB

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