a motorboat whose speed is 9km/hr in still water goes 12km downstream and comes back in total Time of 3hr .find the speed of stream.explain the situation when speed of the stream is more than the speed in still water.
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let speed of stream =x km/h
a/c to question
upstream time + downstream time =3hour
12/(9+x) + 12/(9-x)=3
12 {9-x+9+x}/(81-x^2)=3
12 x 18 =3 (81-x^2)
72=81-x^2
x^2=9
x=+_3
but speed isn't negative
so x =3 km/h
hence speed of stream is 3km/h
situation when speed of stream is greater then speed of motaboat
===================
=> motaboat never reaches at just opposit e side .
for minimum drift======
x=d (x/Scosec@ + cot@)
where x is speed of stream and S is speed of motorboat
dx/d@=0 for x===> min
[cos@ = (-x/S) ] condition.
a/c to question
upstream time + downstream time =3hour
12/(9+x) + 12/(9-x)=3
12 {9-x+9+x}/(81-x^2)=3
12 x 18 =3 (81-x^2)
72=81-x^2
x^2=9
x=+_3
but speed isn't negative
so x =3 km/h
hence speed of stream is 3km/h
situation when speed of stream is greater then speed of motaboat
===================
=> motaboat never reaches at just opposit e side .
for minimum drift======
x=d (x/Scosec@ + cot@)
where x is speed of stream and S is speed of motorboat
dx/d@=0 for x===> min
[cos@ = (-x/S) ] condition.
ganicutie:
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