Specific questions/explanations

[appianway]

Thought I'd start this thread in case anyone has any specific questions they'd like explained or answered... it's a bit hard to trawl through the plethora of posts in the other thread

[qwertyda2nd]

Question 3\4 about the two masses, the other thread is all round the place.

[dyaner]

Question 3\4 about the two masses, the other thread is all round the place.

That question messed me up, just 5 minutes before the exam finished.

[coletrain]

do u think the examiners will give say... 1.5 marks out of 4 if u show working out?

[appianway]

I'm not quite sure what the actual question is, so I'll try and explain it without really knowing... might make a few careless mistakes but this is the general gist

So if you have two masses, and one's over a ledge, this is what will happen.

Both masses must move with the same acceleration as the length of the string is conserved. Denote this acceleration as a.

Denote the mass hanging over the ledge as M. Denote the mass resting on a tabletop as m.

Resolve the forces on M:

Mg-T=Ma

However, the tension force is the only force acting on m, so T=ma
Mg-ma=Ma
Mg = a(M+m)
Thus a = Mg/(M+m)

Then to find the force, multiply m by a. Tension should be the same or something.

I may have misunderstood the question though... I haven't seen it or a diagram...


And yes, marks are allocated for working.

[coletrain]

And yes, marks are allocated for working.

HOPE REMAINS

[m@tty]

What about consequential marks? Is Physics the same as Chem in that you can get full marks by using an already punished wrong answer from a previous question? So you get a wrong, then b uses a . You get the wrong answer for b because of the mistake in a. Do you get full marks for b?

[appianway]

I think you should, as you won't be penalised twice for the same mistake.

[coletrain]

I think you should, as you won't be penalised twice for the same mistake.

MORE HOPE

[m@tty]

Cool. I think maths is different though, that's why I was unsure...

[appianway]

Maths is maths though

Oh, and if you guys have any more questions, please post them! It's better to do them properly than to see what the most common response is... just make sure that you explain the question properly, and I'm sure someone (myself or someone else) will answer

[schnappy]

If your workings are correct... or you state something that's correct. They don't just hand out mark's cos you know how to write down arbitary numbers.

[Kai]

The banked corner question!
you had to find the angle of banking if v = 10m/s and r = 100m i think.
anyway apparently the answer is 5.7 degrees
someone explain?

[m@tty]

If your workings are correct... or you state something that's correct. They don't just hand out mark's cos you know how to write down arbitary numbers.

I was speaking of cases where the ONLY thing wrong is the value previously found(erroneously). So your working and everything is exact.

[appianway]

The acceleration contributed by the banking is gtan(theta). You can work this out by finding the component of the normal force acting towards the centre. From there, you just rearrange to find inverse tan.