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The physics a2 megathread

OP

This shouldn't be hard. While I'm perfectly capable of answering the question, I just want to check a couple of things. Am I right to say that the normal contact force at A is 0? And just what is going on at B? At every other point on the circumference, I can see that either the weight or the normal contact force caused by a component of the velocity is sufficient as a centripetal force. However at B, both the weight and the velocity aren't in the direction of the drum's walls, so I can't see how the net force can be directed towards the centre of the circle (I can't even see how there can be a contact force), help?

It's not correct to say contact f at a is 0. The sock is clinging to the wall so the contact force can be zero or more. But not enough information is given to decide which is true here. However the contact force at a is minimum.

if you consider it, the drum is rotating downwards and towards the left at point b. Weight acts downwards, so what causes the drum to move towards the left? There should be a contact force at b if weight is less than cforce. But in any case weight is not more than cf at any point since the sock clings to the walls.

The force providing centripetal force is the push of machine's wall on the sock at b.

(edited 9 years ago)

Reply 41

thebrahmabull

OP

14

Can anyone solve this problem? I attached it here. It's from the edexcel a2 students book.

2015-03-11 21.19.13.jpg164.7KB

Reply 42

Omghacklol

8

Original post by Stonebridge

If you have a specific problem related to a theory topic, it's best if you post it as a separate thread in study help. It will get lost here in a long thread. In addition, most of the senior helpers, myself included, will probably not be looking in this thread and so won't see the questions.

In addition, I've made this thread "sticky" so it will now stay at the top of the forum in a different colour and not sink down.

Hi, could you please explain why in http://qualifications.pearson.com/co...e_20110621.pdf

2 is A

and also why in http://qualifications.pearson.com/co...e_20110127.pdf

3 is B. Thanks very much in advance.

Reply 43

TaraStilton

Can any really good A2 Physicists please

describe and explain the differences between the interference pattern from double-slit and diffraction grating?

Thank you in advance.

PLEASE HELP!

Reply 44

BP_Tranquility

5

Original post by thebrahmabull

Can anyone solve this problem? I attached it here. It's from the edexcel a2 students book.

Did you find out how to do it? I can't work out how to answer it since it doesn't even say if it's an elastic or inelastic collision

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Reply 45

langlitz

17

Original post by thebrahmabull

Can anyone solve this problem? I attached it here. It's from the edexcel a2 students book.

Original post by BP_Tranquility

Did you find out how to do it? I can't work out how to answer it since it doesn't even say if it's an elastic or inelastic collision

p_1=p_2+p_3

\sqrt{2m_nE_1}=\sqrt{2m_pE_2}+ \sqrt{2m_nE_3}

Rearrange for

m_n

Spoiler

(edited 9 years ago)

Reply 46

krnwright

Hey can anyone help me in answering this Unit 4 question, I know the answer is C but I'm not sure how to get there? :smile:

Original post by krnwright

Hey can anyone help me in answering this Unit 4 question, I know the answer is C but I'm not sure how to get there? :smile:

Welcome to TSR physics.

It's better to post questions needing help like this one in the main Study Help section. It will get lost in this long thread.

Apply the formula for electric potential at a point a distance 40mm from a charge for both charges and add the two values you get together.

(edited 9 years ago)

Reply 48

l1lvink

11

Original post by krnwright

Hey can anyone help me in answering this Unit 4 question, I know the answer is C but I'm not sure how to get there? :smile:

Try posting it here
http://www.thestudentroom.co.uk/showthread.php?t=3047347&page=48

Reply 49

NekoJyo

9

In CCEA A2 Unit 1 in the topic thermal physics we have to know an equation: PV=(1/3)Nm<c^2>
But I don't know what N or m are
Is N the number of molecules?
And is m the mass of the gas?

Reply 50

sefulK

Can anybody explain to me how this question should be answered and capacitor questions in general.

Posted from TSR Mobile

1432382104345.jpg35.7KB

Reply 51

Trupac

5

Help!!
The emf changes direction, hence the second pulse is negative. What i don't get is why it changes direction

Reply 52

NDVA

8

Original post by Trupac

Help!!
The emf changes direction, hence the second pulse is negative. What i don't get is why it changes direction

The coil is 'going in' at A but 'going out' at B so the emf induced should be different i.e change in direction :smile:

Reply 53

Trupac

5

Original post by NDVA

The coil is 'going in' at A but 'going out' at B so the emf induced should be different i.e change in direction :smile:

Cheers mate!

Reply 54

BP_Tranquility

5

Just did that paper but Why is there a section in the graph which has no emf induced (along the x axis) ?

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Reply 55

iceangel8

14

Original post by BP_Tranquility

Just did that paper but Why is there a section in the graph which has no emf induced (along the x axis) ?

Posted from TSR Mobile

When it is in the centre of the magnet there is no change in flux so no emf induced.

Reply 56

BP_Tranquility

5

Original post by iceangel8

When it is in the centre of the magnet there is no change in flux so no emf induced.

For there to be a change of flux, do the field lines have to be different spaced in front of and behind the magnet ?

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Reply 57

langlitz

17

Original post by BP_Tranquility

For there to be a change of flux, do the field lines have to be different spaced in front of and behind the magnet ?

Posted from TSR Mobile

When you are between the magnets then the magnetic field is constant so there is no changing magnetic flux to induce an emf. When you reach the end of the magnets then the magnetic field drops of as you move further away.
Don't think of it in terms of magnetic field lines

Reply 58

Rhetorical Hips

14

The direction of the force on a charged particle moving through a magnetic field - does it depend on whether the charge is positive or negative (i.e. positrons deflected opposite direction to electrons) are is it only dependent on the SIZE of the charge?

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Reply 59

NDVA

8

Original post by Rhetorical Hips

The direction of the force on a charged particle moving through a magnetic field - does it depend on whether the charge is positive or negative (i.e. positrons deflected opposite direction to electrons) are is it only dependent on the SIZE of the charge?

Posted from TSR Mobile

The direction of the force does depend on the sign (positive or negative) of the charge but it does not depend on the size of the charge. However the magnitude of the force does depend on the size of the charge (size as in +1 or +5) :smile:

The physics a2 megathread

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