[hassantahir]

Hi, I've just started M2 and the first chapter is driving me nuts. can someone please help me with this question. photo attached. Question 7B, I keep on getting 31.9N as the answer but it is 34.5N. my working is included (even though its most likely wrong). thanks and please include how you got the answer.

[raheem94]

(Original post by hassantahir)
Hi, I've just started M2 and the first chapter is driving me nuts. can someone please help me with this question. photo attached. Question 7B, I keep on getting 31.9N as the answer but it is 34.5N. my working is included (even though its most likely wrong). thanks and please include how you got the answer.

I get the answer as 45.9N. I don't know how the actual answer is 34.5N.

You haven't marked the normal reaction from the floor and fence on your diagram.

[hassantahir]

Well that the answer at the back:34.5N picture of working?, EDIT: yes i wasnt meant to include it in my photo as the diagram was wrong but the real diagram does include these reaction you have mentioned. have you got the answer?

[raheem94]

(Original post by hassantahir)
Well that the answer at the back:34.5N picture of working?, EDIT: yes i wasnt meant to include it in my photo as the diagram was wrong but the real diagram does include these reaction you have mentioned. have you got the answer?

I am getting the answer as 45.9N. Do your book answers usually contain mistakes?

I can't be sure if i am correct, because i haven't done M2 from a long time.

[hassantahir]

(Original post by raheem94)
I am getting the answer as 45.9N. Do your book answers usually contain mistakes?

I can't be sure if i am correct, because i haven't done M2 from a long time.

Well i just started m2 so dont know about this book but the same series (C1, C2, C3, C4, M1) dont usually include mistakes. Are you using moments to answer the question? what are you getting as the perpendicular distance for the mass to your moment point?

[raheem94]

(Original post by hassantahir)
Well i just started m2 so dont know about this book but the same series (C1, C2, C3, C4, M1) dont usually include mistakes. Are you using moments to answer the question? what are you getting as the perpendicular distance for the mass to your moment point?

I am doing it in this way:

I am taking moments about the point where the normal reaction from fence and ground intersect.
So i do it in this way,
F x 1.6 = 10g x 1.5cos60
So i get F=45.9N.

[ghostwalker]

34.5N is the correct answer (34.453125N to be exact).

Your diagram is missing:

A vertical normal reaction at the base of the pole, and also a normal reaction at the point of contact of the fence and pole, this latter reaction will be perpendicular to the line of the pole.

To solve:

Take moments about the base of the pole of find the normal reaction at the top of the fence, and then resolve horizontally.

[hassantahir]

Is there a horizontal component of weight? i dont see how your getting 1.5cos60

[raheem94]

(Original post by ghostwalker)
34.5N is the correct answer (34.453125N to be exact).

Your diagram is missing:

A vertical normal reaction at the base of the pole, and also a normal reaction at the point of contact of the fence and pole, this latter reaction will be perpendicular to the line of the pole.

To solve:

Take moments about the base of the pole of find the normal reaction at the top of the fence, and then resolve horizontally.

You are absolutely correct, i was taking the reaction from the fence to the pole as horizontal due to which i was getting a wrong answer.

If you have some time, can you please go through the below linked thread:
http://www.thestudentroom.co.uk/show...5#post36476785

I have some confusion in post number 22 of that thread.

[hassantahir]

thank you so much, i understand now. do you recommend any books to learn from?