Tgr (h) P1

Steoob

what did ye think? i didn't think it was 2 bad, i did the first 4 questions and only had trouble with question 1 part c and the tangent plane in solids in contact... reckon i got everything else pretty perfect

ZorbaTehZ

Very happy.
Did Q1 Q3 Q5 Q7. Q1C wasn't too bad, I used intersecting cones to get the line. Q3C point of contact between plane was ok. I did my tangent through the original cone since I wanted it to intersect the vert on the page . Q5 rather unusual, but still not too bad. Q7 pretty typical question there tbh, the phrasing for the circumcentre was a bit obtuse (pardon the pun).

On Q3B, were people's cone C pretty big? Mine was higher than cone A and had a radius of about 40-50mm.

For meh,
Q1B Dihedral Angle: 19-21/159-161 degrees
Q1D 9.5mm

sallyally

i done q1, q4, q5 n q6...
q1 was typical , fine really i got 9mm for da distance between da lines..i kinda made a mess out of q4....q5 was lovely easiest by far... n q6 was ok..(B) was iffy but i tink i got it

fingers crossed fro paper 2

Steoob

ZorbaTehZ wrote:

Very happy.
Did Q1 Q3 Q5 Q7. Q1C wasn't too bad, I used intersecting cones to get the line. Q3C point of contact between plane was ok. I did my tangent through the original cone since I wanted it to intersect the vert on the page . Q5 rather unusual, but still not too bad. Q7 pretty typical question there tbh, the phrasing for the circumcentre was a bit obtuse (pardon the pun).

On Q3B, were people's cone C pretty big? Mine was higher than cone A and had a radius of about 40-50mm.

For meh,
Q1B Dihedral Angle: 19-21/159-161 degrees
Q1D 9.5mm

i got 155 degress for the diherdral and 8 mill for the true length... tho its just drawing error we'll both get full marks...

ya the cone c in Q3 is big, a nice bit bigger than the cone a

DtotheK

my cone was quite big... didn't measure it tho. the plane bit i wasnt sure about and guessed, and Q1c is always a stab in the dark guess for me but apart from those it was fine!!

Hope paper 2 is ok aswell and come on A1!!!

Oh and i got 9 millimetres for Q1 true length, which is basically what all of ye got!!

The interpenetrating solids was a wee bit tricky cause you had to get 4 points from the 3D model and transfer them to the plan but i think i got them.
That page got so dirty for some reason and i had to spend f.ckin ages to rub the gunk off it!!

madnirvana

i couldnt get the tangent plane:mad:

and 1 c

rest was good

hopefully A1..plzplzplzplplz

paper 2:eek:

sd123

couldn't completely work out how to get the traces of the plane in solids in contact, made a good attempt at it though so has to be worth bout 3/4 marks! the cycloid q and oblique plane question was lovely though, while q 1 was typical, i got 9mm, someone else i asked got 7mm but i'm sure they'll probably allow for bout 2-3 mm for inaccuricies . ok paper, with a few things you had to think bout.;)
I did the only 4 quesions my teacher covered properly with us, Qs 1,2,5 and 7.!!!:mad:

DtotheK

Q1c is only worth bout 6 marks(got it wrong in the mocks) and the tangent plane wont be worth a HUGE amount so if al else goes/went good an A1 is well within reach!!

I hope...

Steoob

is Q1c even possible to learn for??? ive never gotten it right and its usually the only thing i mess up... but now apparantly noone gets it.... its too hard i reckon... off the course NOW (not that i care coz im finished )

DtotheK

yeah Q1c there's like 5 or 6 possibilities for that question but i never learnt them off i just do what makes sense in my head... which rarely works for that part. but it's worth so little it's not really worth it!

Fuzzy_Dunlop

Are people sure that the traces for the solids in contact were even possible, everyone in my class had them go waaaaaay of the page, and putting it on the opposite side of the cones isn't right i don't think

ZorbaTehZ

playa3 wrote:

Are people sure that the traces for the solids in contact were even possible, everyone in my class had them go waaaaaay of the page, and putting it on the opposite side of the cones isn't right i don't think

Why is it not right then?

If you placed the tangential plane on the bottom side then no it was not possible to find the vertical trace. Thats why I placed it on the other side like I said.

EDIT: That doesn't mean to say that you actually had to find the vertical trace though.

Steoob

what i did was i got the cone c, and alos put a cone around the point of contact between c and the hemisphere.. it made sense due to the only other way i could think of had the construction going off the page

ZorbaTehZ

Steoob wrote:

what i did was i got the cone c, and alos put a cone around the point of contact between c and the hemisphere.. it made sense due to the only other way i could think of had the construction going off the page

Nice one!, wouldn't have thought of that myself. However in nearly all the tangential planes questions, there are a number of possibilities, so I think we will all still get the full marks, as long as the proper construction was used.

Fuzzy_Dunlop

Alright then, its just that when i did it on the opposite side and got the vertical trace, it was going the opposite direction so would never have touched the hemisphere

Feddd

The tangent planes went through the middle of the hemi and new cone and in plan appeared as a tangent to the circle below the hemi generated by the second cone. Although, I think technicly if you made it tangental to the new cone and rest on the edge of the top of the hemisphere its still a tangental plane? And the point of contact between the hemi and plane is simply the poc between the hemi and new cone, right?

And the whole point of 1C is to avoid rote learners doing that question because without it it would be almost the same year in year out.

ZorbaTehZ

Feddd wrote:

The tangent planes went through the middle of the hemi and new cone and in plan appeared as a tangent to the circle below the hemi generated by the second cone. Although, I think technicly if you made it tangental to the new cone and rest on the edge of the top of the hemisphere its still a tangental plane? And the point of contact between the hemi and plane is simply the poc between the hemi and new cone, right?

And the whole point of 1C is to avoid rote learners doing that question because without it it would be almost the same year in year out.

Yup, 'tis indeed.
As for the second point, thats right if you put the plane through the point of contact between them both. If you placed it on either of one of the sides then all you had to do was draw a line perpendicular from the center of the hemisphere to the plane's horizontal trace, and the point simply lay where that line passed the edge of the hemisphere.

1C is for determining the "spatial understanding" of a student, i.e. their ability to construct the situation in their head, and also crucially to determine if they have a fundamental understanding of each of the objects/constructions and their interactions. So, ofc, this does ward off against "rote learners".

Just remembered, how did people determine the starting point of the involute in Q5? I used 15 degree arcs, compassed them onto MP then the end bit I compassed back onto the circle. Rather crude, but I think I should get all the marks tbh.

EDIT: Typo

Feddd

Heres a rough sketch of my tangent planes using the one that gos through the middle. For the point of contact I looked along the green line in plan for an edge view of the plane(I know there was an easier way but I had plenty time and it looked better! ):

ZorbaTehZ

The green line isn't meant to intersect the bottom of the cone mate. It's meant to be a tangent to it.

Feddd

ZorbaTehZ wrote:

the point simply lay where that line passed the edge of the hemisphere.

Just remembered, how did people determine the starting point of the involute in Q5? I used 15 degree arcs, compassed them onto MP then the end bit I compassed back onto the circle. Rather crude, but I think I should get all the marks tbh.

If the poc between the hemi and tangent plane was on the edge, wouldn't that mean the plane would need to be verticle? Unless I misunderstood what you meant as edge.

And I did the same for Q5. just worked the involute construction backwards taking the arc length from MP each time.

Feddd

ZorbaTehZ wrote:

The green line isn't meant to intersect the bottom of the cone mate. It's meant to be a tangent to it.

Yeh, had it tangental in my exam, just hard to get circles right in paint and didn;t notice it.

ZorbaTehZ

kk

As for the other point about the vertical plane, no. A vertical plane is one of the possibilities. You must remember that it's a hemisphere were talking about here, so the range of possibilities for a tangent to a point on the edge of the hemisphere are vertical at the point and all the other possibilities leaning *over*the hemisphere, since they're still a tangent too.
I see that thats a rather crap explanation, maybe some else can do better.

Feddd

ZorbaTehZ wrote:

kk

As for the other point about the vertical plane, no. A vertical plane is one of the possibilities. You must remember that it's a hemisphere were talking about here, so the range of possibilities for a tangent to a point on the edge of the hemisphere are vertical at the point and all the other possibilities leaning *over*the hemisphere, since they're still a tangent too.
I see that thats a rather crap explanation, maybe some else can do better.

But considering it was a tangent plane to the Cone does it not have to have the same pitch as the cone?

Feddd

ZorbaTehZ wrote:

kk

As for the other point about the vertical plane, no. A vertical plane is one of the possibilities. You must remember that it's a hemisphere were talking about here, so the range of possibilities for a tangent to a point on the edge of the hemisphere are vertical at the point and all the other possibilities leaning *over*the hemisphere, since they're still a tangent too.
I see that thats a rather crap explanation, maybe some else can do better.

hang on, I see the misunderstanding here. You didn't do your plane through the middle of the cone and hemi and hence your poc was on the edge. I did mine through the middle and got a poc on the curved surface which would mean that the edge doesn't come into account.

DtotheK

My horizontal tangent just went through the centre of the cone in plan and a small arch inside the other circle (got by a line parallel to cone against sphere in elecation, and brought down)

I had 2 possible "answers" one of which would have gone miles off the page.

Is what i did remotely right??

ZorbaTehZ

Feddd wrote:

hang on, I see the misunderstanding here. You didn't do your plane through the middle of the cone and hemi and hence your poc was on the edge. I did mine through the middle and got a poc on the curved surface which would mean that the edge doesn't come into account.

Hence why I said:

ZorbaTehZ wrote:

As for the second point, thats right if you put the plane through the point of contact between them both. If you placed it on either of one of the sides then all you had to do was draw a line perpendicular from the center of the hemisphere to the plane's horizontal trace, and the point simply lay where that line passed the edge of the hemisphere.

I suppose maybe I was a little bit ambiguous in the language I used, but no, I didn't put my plane through the point of contact, rather on the "top" side of the objects.

@Dtothek
Hmmm, I don't know about that mate, it went through the center of cone C in plan? It should be tangential to the base of the cone in plan, but tbh from the sounds of the construction you used I think you will probably get most of the marks. TG is really good in that respect, the marks are broken down into like 2s and 3s so it's easy to pick up a lot of marks even if something is quite wrong in one aspect.

DtotheK

**** yeah your right.. ****!
but cheers at least i'm not questioning it and actually know the answer!

Hopfully i will get most marks!!!!
i seriously have to kick some ass tomorrow , i pretty much have to get an A.. cant afford to cock up

daraghc

DtotheK wrote:

That page got so dirty for some reason and i had to spend f.ckin ages to rub the gunk off it!!

Should've washed your setsquares before the exam, I did;)

DtotheK

i had them perfectly ready.. but i think it was a crap quality HB pencil that ruined them... have to clean them now, at least i learnt my lesson!!

anyway sopranos on now so good luck everyone tomorrow!

Fool 5000

Question 1 !!:mad: need i say more