# BoS trials Maths and Chemistry 2020 (1 Viewer)

##### -insert title here-
Aye good job to the person who got 72! Well done to everyone else as well.

Seems question 16 destroyed everyone this year.
personally, 16 (a) is the harder question for me, because i understand irrationality proofs like physicists understand newtonian mechanics

#### Drdusk

##### π
Moderator
personally, 16 (a) is the harder question for me, because i understand irrationality proofs like physicists understand newtonian mechanics
Imagine having to prove irrationality when you can just plug it into a calculator. QED.

#### Trebla

I reckon Q16a) is probably as challenging as you can get when it comes to resisted projectile motion, mainly because a sneaky trick is needed to get part (ii) out, otherwise you're going to be stuck. Most textbook or past exam questions (of which there are very few) are far more straightforward.

##### -insert title here-
Imagine having to prove irrationality when you can just plug it into a calculator. QED.
numbers have an end

therefore all decimal expansions terminate

therefore all real numbers are rational

this is satire btw

#### beetree1

##### Well-Known Member
Dont be shy who got the top mark?

#### terryz

##### New Member
All jokes aside it is not me, but someone I know. He does not want people to know as he is a humble man. Keep working hard and maybe you can see him at NESA Party!

#### ultra908

##### Active Member
All jokes aside it is not me, but someone I know. He does not want people to know as he is a humble man. Keep working hard and maybe you can see him at NESA Party!
is there even gonna be a nesa party with covid

#### sysysysy

##### New Member
Hi, can someone explain to me why it's N=mg cos theta and not mg=N cos theta for Q14a(i)? and also why is it suddenly sin theta for a(ii)?

This is for extension 2 paper btw, thanks!

#### YonOra

##### Well-Known Member
When can we expect the Ext 1 answers?

#### beetree1

##### Well-Known Member
Hi, can someone explain to me why it's N=mg cos theta and not mg=N cos theta for Q14a(i)? and also why is it suddenly sin theta for a(ii)?

This is for extension 2 paper btw, thanks!
check their solutions

#### Trebla

Hi, can someone explain to me why it's N=mg cos theta and not mg=N cos theta for Q14a(i)? and also why is it suddenly sin theta for a(ii)?

This is for extension 2 paper btw, thanks!
The direction in which you resolve the forces is not horizontal/vertical. It is parallel/perpendicular to the inclined surface. This is because the net force of the object is parallel to the inclined surface.

#### sysysysy

##### New Member
The direction in which you resolve the forces is not horizontal/vertical. It is parallel/perpendicular to the inclined surface. This is because the net force of the object is parallel to the inclined surface.
Ohh I get it now, thank you

#### Charles

##### New Member
Are the solutions to the BOS chem 2020 trial out yet?

#### Trebla

Are the solutions to the BOS chem 2020 trial out yet?
Not yet. Maths is taking priority at this stage as their exams are sooner. Chemistry should be out around a week after.

#### Trebla

Just marked Q12 of Maths Ext1 and have some feedback on Q12e)i)

The question asked students to prove a given vector relationship between A, B and P given that

$\bg_white \dfrac{AP}{BP}=\dfrac{1-\mu}{\mu}\quad 0<\mu<1$

A very common response from students was to assert that

$\bg_white \overrightarrow{AP}=\left(\dfrac{1-\mu}{\mu}\right)\overrightarrow{BP}$

This is not correct because the given ratio above is purely related to vector magnitudes. To convert to vector equations, you need to take into consideration both the magnitude AND the direction of the vectors. Notice that vector AP does NOT point into the same direction as BP (as P lies in the interval AB) so they cannot be related by a positive scalar. Many students attempted to fudge the result when they realised the algebra did not work out from this assertion. Better responses carefully considered the directions that the vectors were pointing and often related the directions of AP and AB.

#### Charles

##### New Member
Not yet. Maths is taking priority at this stage as their exams are sooner. Chemistry should be out around a week after.
ok thanks

#### HeroWise

##### Active Member
seemed like the marker had a great time marking q16!!! ;D
ITS GUO EN SHAO

#### OnJob

##### New Member
Does anyone know when EXT 1 answers will be released?