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Dynamics help

With this question, why is R equal to 10cos30 + 12sin30 instead of R + 12sin30 = 10cos 30 because in the past I have come across a question which used the second principal
(edited 2 years ago)
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Because 12N is going towards the plane.
Original post by CaptainDuckie
Because 12N is going towards the plane.

Could you further explain that please? Also is the second principle that I mentioned valid for some certain cases
Original post by Lina_Amiour
Could you further explain that please? Also is the second principle that I mentioned valid for some certain cases



Your second case mainly applies when the object is being pulled up a plane, so when resolving, using SOHCAHTOA, the opposite will be the same direction as R. So north west.
So as per the mark scheme: R+12sin30=12cos30


But since you have this force keeping this block in equilibrium, when resolving, the force that is opposite will go towards the opposite direction of R as it’s going towards the plane.
As per the mark scheme: R= 12cos30+12sin30

this video explains it better than me
o

Original post by CaptainDuckie
Your second case mainly applies when the object is being pulled up a plane, so when resolving, using SOHCAHTOA, the opposite will be the same direction as R. So north west.
So as per the mark scheme: R+12sin30=12cos30


But since you have this force keeping this block in equilibrium, when resolving, the force that is opposite will go towards the opposite direction of R as it’s going towards the plane.
As per the mark scheme: R= 12cos30+12sin30

this video explains it better than me

ok, thank you ever so much :smile:

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