IIT JEE , AIEEE Forum - Physics , Mechanics

gpranay123

${v}_{b}\rightarrow velocity of boat{v}_{r}\rightarrow velocity of river$

let motor boat reach a point B then return and pass the raft at point C after a time t

${v}_{b}+{v}_{r}*1=AB\\({v}_{b}-{v}_{r})t=BC\\$

AD+BC=AB-AC D be the point down stream where AD is the distance travelled in 1hr

$AD={v}_{r}*1\\DC=({v}_{r})t\\$

by solving above equations we get t=1hr

for AC (V_r)(1+1)=6 V_r=3kmph