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Question 10 from 78 paper (1 Viewer)

rsingh

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Hey guys, I need some help doing this question, it looks more like a 3u question then 2u, but nevertheless, it's q10 from the 1978 paper.

Two cares, respresented by pts A and B, are travelling due east and north respectively along two road represented by two straight lines intersecting at O. At a certain instant, car A is 2 km west of O and car B is 1km south of O, the former travelling at a constant speed of 1km/minute and the latter at a constant speed V km/minute.


(a) What value of V will cause a collison?
(b) Prove that, in the course of motion, the MINIMUM distance between the cars is
|2V-1|/(v^2+1)^0.5 km.
(the top is aboslute value of 2V-1 and the bottom is square root of v squared + 1.
 

mattchan

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Umm. Lets see

a) Car A is travelling at 60km/hr

S = D/T
60 = 2 / T
Therefore T = 1/30 hours = 2 minutes

Car B is travelling at 60V km/hr
S = D/T
60V = 1 / (1/30)
V = 1/2.

Therefore, Car B must travel 0.5 km/min to crash with Car A at Point 0
 
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rsingh

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Thanks for that.
Does anyone have a solution to the second bit?
 

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