OCR (non mei) M1 Friday 17th June 2016

Reply 80

Mattyreds999

Original post by daniellon

Cosine rule in the formula booklet?

i got 97.2, you guys sure your not mistaking it for a different answer?

Reply 81

G_8

1

Original post by Snicherz

forgot to work on time on question 1 :unimpressed:

, 2 marks off?

(also what was the question on the contact force asking?)

It was just asking you to isolate P as a single component and then calculate the contact force exerted on it by the plane. So you just had to use R and F (which I think you establish in the part of the q before this) and then use pythagorus.

Reply 82

Mattyreds999

Original post by Furthermaths100

You are wrong, put one of the forces due north, and the other with 97.18 and resolve to get the resultant and it won't be 6N.

dude, the answer is 97.18

Reply 83

G_8

1

Original post by Mattyreds999

dude, the answer is 97.18

Would you mind explaining how you got this answer?

Reply 84

duncanjgraham

3

Original post by Mattyreds999

dude, the answer is 97.18

please can you explain to me how I'm wrong in my solution>>>??

Reply 85

Mattyreds999

Original post by G_8

Would you mind explaining how you got this answer?

you have two forces acting on a particle, top to tail them, work out angle in-between them using cosine rule seeing as you know a 3 sides

Reply 86

Mattyreds999

Original post by duncanjgraham

please can you explain to me how I'm wrong in my solution>>>??

To be honest man, it was like a 2 mark question for that part, from the amount of working you needed to do, thats a slight hint that you may have over complicated it. who knows, maybe its right, my gut tells me that 97.2 was right though. we'll just have to see

Reply 87

duncanjgraham

3

Original post by Mattyreds999

To be honest man, it was like a 2 mark question for that part, from the amount of working you needed to do, thats a slight hint that you may have over complicated it. who knows, maybe its right, my gut tells me that 97.2 was right though. we'll just have to see

it was more than 2, i think 3. I've done it in a slightly unconventional way that's all.

Reply 88

Mattyreds999

Original post by Mattyreds999

dude, the answer is 97.18

if you put one due north and the angle between this 4n force and the other as 97.18 degrees and then use cosine rule. you will find the reultant to be six my friend

Reply 89

Furthermaths100

1

Original post by Mattyreds999

dude, the answer is 97.18

The answer cannot be 97.18 as it does not work if you resolve the forces to get the resultant force. Put one of the 4N forces vertical and the other at 97.18, resolve and you will get a vertical as 4-4sin7.18= about 3.5, and horizontal (which is correct either way) as 4cos7.18 which is about 3.96N. Are you therefore saying 3.5^2 + 3.96^2 equals 36? (6^2)
Do the maths, it doesn't work! The answer is 100% 82.8.

Reply 90

duncanjgraham

3

Original post by Furthermaths100

The answer cannot be 97.18 as it does not work if you resolve the forces to get the resultant force. Put one of the 4N forces vertical and the other at 97.18, resolve and you will get a vertical as 4-4sin7.18= about 3.5, and horizontal (which is correct either way) as 4cos7.18 which is about 3.96N. Are you therefore saying 3.5^2 + 3.96^2 equals 36? (6^2)
Do the maths, it doesn't work! The answer is 100% 82.8.