M1 Help PLZ Im Badly In Need Of the HElp

[bahaa spain]

HEllo every body

Im preparing for my M1 exam EDEXCEL that will be done on 19-01-2010 ... anyway I started with my pastpapers and then I went to solomon

exactly in Paper L

Fisrst Question:

two trains A and B leave the same station O at 10 am and travel along a strasight horizntal tracks. A travels with constant speed 80 km/h due east and B Travels with 52 km/h in the direction (5i + 12j)

(a) show that the velocity of B is 20i+48j

(b) find the displacement vector of B from A at 10.15 am


given that the trains are 23km apart t minutes after 10 am

c) find the value of t to the nearest whole number



((((((((((((((( please any body who wants to help me give me full explanation for each and every step cuz i cant understand the markscheme))))))))))))))))

[astarmathsandphysics]

sqrt(5^2 +12^2)=13
times by 4 to get 52 so times 5i+12j by 4 to get 20i+48j
b)B travels for 1/4 hour so displacement =1/4v=5i+12j
c)23=sqrt((x_b -x_a)^2 +(y_b-y_a)^2)
23^2 =(5t--80t)^2+(12t)^2 =(85t)^2 +144t^2 =7369t^2 so t^2 =529/7369=0.0718 hours
t=sqrt(0.0718) =0.267 hours =60*0.267-16 mins

[Khey [Rainbow]]

How was ur xam?