IIT JEE , AIEEE Forum - Physics , Mechanics

kghedriu

1)Suppose two particles have position vectors r2 and r1 and their velocities are v2 and v1 (note that r2, r1 , v2, v1 are vectors)..collide is:

r2-r1/ [r2-r1] = v2-v1/[v2-v1]

where [x] denotes magnitude of x.....

2) in the general river- swimmer case....

let Vmg => vel of man w.r.t ground

Vmw=> vel of man w.r.t water

Vwg => vel of water w.r.t ground..

then....the conditions for:

(i) zero drift is: Vwg is perpendicular to Vmg

(ii) minimum time is: Vmw is perpendicular to Vmg

(iii) non-zero min drift is: Vmw is perpendicular to Vmg

the case (iii) arises when vel of man is less than vel of water flw..