MS Missing some forces

Hi all,

On q3ii, I understand that we have to resolve the forces to get magnitude of the force exerted on Beam A at the wall. Link to Paper: http://pmt.physicsandmathstutor.com/download/Maths/A-level/M2/Papers-OCR/June%202012%20QP%20-%20M2%20OCR.pdf

But the MS doesn't seem to be taking account of the contact force between the rod and the wall.

Link to MS: http://pmt.physicsandmathstutor.com/download/Maths/A-level/M2/Papers-OCR/June%202012%20MS%20-%20M2%20OCR.pdf

Is it because the rod is 'light' so we are taking contact force as negligible?

Thanks!

Reply 1

arjibarji123

10

If you aren't given a mass of the Rod then state in your assumptions that it is massless.

Reply 2

Snoozinghamster

21

Original post by ChemBoy1

Hi all,

On q3ii, I understand that we have to resolve the forces to get magnitude of the force exerted on Beam A at the wall. Link to Paper: http://pmt.physicsandmathstutor.com/download/Maths/A-level/M2/Papers-OCR/June%202012%20QP%20-%20M2%20OCR.pdf

But the MS doesn't seem to be taking account of the contact force between the rod and the wall.

Link to MS: http://pmt.physicsandmathstutor.com/download/Maths/A-level/M2/Papers-OCR/June%202012%20MS%20-%20M2%20OCR.pdf

Is it because the rod is 'light' so we are taking contact force as negligible?

Thanks!

Yeh
Also try just focusing on the forces on the beam. It makes it easier to focus on the bits the question cares about

Reply 3

ghostwalker

17

Original post by ChemBoy1

Hi all,

On q3ii, I understand that we have to resolve the forces to get magnitude of the force exerted on Beam A at the wall. Link to Paper: http://pmt.physicsandmathstutor.com/download/Maths/A-level/M2/Papers-OCR/June%202012%20QP%20-%20M2%20OCR.pdf

But the MS doesn't seem to be taking account of the contact force between the rod and the wall.

Link to MS: http://pmt.physicsandmathstutor.com/download/Maths/A-level/M2/Papers-OCR/June%202012%20MS%20-%20M2%20OCR.pdf

Is it because the rod is 'light' so we are taking contact force as negligible?

Thanks!

The weight of the rod isn't relelvant to the question. You're only interested in the forces acting on the beam.

If you try and look at the beam and rod as a single item, you have a problem in that the weight of the rod is unknown. It may cancel out in some of your working - not checked - but you're at the very least making life harder for yourself.

Reply 4

username3600090

OP

8

Thanks all!

I seem to understand it now :smile:

MS Missing some forces

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