HSC 2012 MX1 Marathon #2 (archive) (2 Viewers)

[Timske]

Re: HSC 2012 Marathon

i have a booklet of past CSSA trials, im sure i can find something

have u done SHM yet?

Nope. Just had a brief lesson on it today at tutor

 

[barbernator]

Re: HSC 2012 Marathon

A man 1.8m tall, standing due east of a street light notices that his shadow is 6.5m long. He walks on a bearing of 150 deg T from his position for a distance of 12 m and now finds his shadow is 9.1m long. Find the height of the street light above the ground level. (in m correct to 1 dp)

 

[Timske]

Re: HSC 2012 Marathon

A man 1.8m tall, standing due east of a street light notices that his shadow is 6.5m long. He walks on a bearing of 150 deg T from his position for a distance of 12 m and now finds his shadow is 9.1m long. Find the height of the street light above the ground level. (in m correct to 1 dp)

This is hard right?

 

[barbernator]

Re: HSC 2012 Marathon

This is hard right?

i guess so, final question in 1988 paper.

 

[Timske]

Re: HSC 2012 Marathon

just want to make sure im on the rite track

 

[RishBonjour]

Re: HSC 2012 Marathon

I got 5.3 ?

my diagram is exactly like timske's

edit:
probably way off. haven't done trig in ages

whats zeee answerrrr.

Ill do the question again lol

 

[barbernator]

Re: HSC 2012 Marathon

zeeeee answer is not zat

 

[barbernator]

Re: HSC 2012 Marathon

just want to make sure im on the rite track

View attachment 25257

that diagram is correct

 

[RishBonjour]

Re: HSC 2012 Marathon

I got the same diagram :/
ill try again later lol

 

[Timske]

Re: HSC 2012 Marathon

Doing it now pretty hard

 

[Timske]

Re: HSC 2012 Marathon

4.7 ?

Edit: 5.125

 

[Nooblet94]

Re: HSC 2012 Marathon

5.9?

Wouldn't be surprised if I'm wrong, my working's rushed and messy

 

[Timske]

Re: HSC 2012 Marathon

don't think im right either lol

 

[Nooblet94]

Re: HSC 2012 Marathon

I'm pretty sure my method is correct... it's just a matter of whether or not I actually did the calculations correctly.

 

[Timske]

Re: HSC 2012 Marathon

how didu do it

 

[Timske]

Re: HSC 2012 Marathon

5.125 !!!!!

 

[Nooblet94]

Re: HSC 2012 Marathon

I'll try describe it, but it's kind've tough without a diagram to point at and whatnot

(h=height of lamp, x=distance to lamp from pos. 1, y=distance to lamp from pos. 2)

I used the two pairs of similar triangles to create two expressions for h in terms of x and y and then equated the two. Rearranged that and found x in terms of y. Then I used the cosine rule in the 12/x/y triangle to get a quadratic in y. Solved for y and then subbed that value back into the expression for h.


(barb, i want teh answer, plz resp0nd)

 

[RishBonjour]

Re: HSC 2012 Marathon

I used the cosine rule too. same method

I got 7.7 now..


Going to stop doing this, have bio assignment.

 

[Timske]

Re: HSC 2012 Marathon

I think nooblet got it

 

[RishBonjour]

Re: HSC 2012 Marathon

yeah, his method seems right