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Help with question in Edexcel M1 textbook

Hello, I am stuck Exercise 3I, question 6 in the Edexcel M1 textbook and even though I have the answer on the solution bank I still do not understand how they got to the answer. Could someone please explain it to me?

I hope that everyone is having a good weekend :smile:

(edited 7 years ago)

Reply 1

rayquaza17

Hello I have moved this to maths for you.

Which part of the solution do you not understand? :smile:

Reply 2

Bunnell

Original post by rayquaza17

Hello I have moved this to maths for you.

Which part of the solution do you not understand? :smile:

Thanks for moving the thread! I'm having trouble with pretty much all of part A - the only thing I understand is why the sum of the forces is equal to 0. :s-smilie:

Reply 3

Kvothe the Arcane

Original post by Bunnell

Thanks for moving the thread! I'm having trouble with pretty much all of part A - the only thing I understand is why the sum of the forces is equal to 0. :s-smilie:

Friction is opposing the movement of the particle up the plane so we know that it's acting down the plane. We can resolve this to be

F \sin \alpha

acting downwards. Note that coefficient of friction is 0.5 and we also know that

F= \mu R

F \sin \theta = 0.5R\sin \alpha

. When you resolve vertically, the only other forces to consider are the reaction force and the weight of the particle.

You now have the algebraic equation with unknown R that's shown in the MS and can go on to solve it.