- #1

mcintyre_ie

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I need a little help with this (B) question:

Find:A girl wishes to siwim across a river 60m wide. The river flows with a velocity q m.s^-1 parallel to the straight banks and the girl swims at a velocity of p m.s^-1 relative to the water. In crossing the river as quickly as possible she takes 100s and is carried downstream 45m.

(I) P and Q

(II)How long will it take her to swim in a straight line back to the original starting point.

Ive done some of the basics here, which i know to be right, including the answers to part 1 - when i tried to bring it further i got answers which were obviously wrong for part 2. This is what I've got so far, any help would be appreciated:

Vr (welocity of river) = q m.s^-1

Vg/r )velocity of girl relative to river) = Vg - Vw

Vg = (pi + qj) m.s^-1

when t = 100s, d = 45i + 60j

P = 60/100 = .6m.s^-1

Q = 45/100 = .45m.s^-1

Vg/r = .6m.s^-1

Vr = .45 m.s^-1