Motor Velocity

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A motorboat going downstream overcame a raft At a point A ;
Ï„=60min later it turned back and after sometime passed the raft at a distance l=6.0km from the point A . Find the flow velocity assuming the duty of the engine to be constant

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2 Answers

283
Sahil Jain ·

Let the speed of motor boat be Vm
let the speed of stream be Vs
For the raft the motot boat downstream goes at a speed of
(Vm + Vs - Vs) = Vm
for upstream = { Vm- Vs - (-Vs)} = Vm
Now since the displacement wrt to raft of the motor boat is zero, time for upstream journey is also 60min
{ since displcement is zero so Vm*60 - Vm*t = 0 so t is 60 Min)
now the speed of raft is same as speedfor the stream
so Vs* ( 60 + 60 )= 6 km
solving we get Vs= 3 km/mi
please check the ans whether it is right or not

535
Aditya Agarwal ·

Let speed of raft(stream) be u km/hr
and speed of motorboat wrt water be v km/hr
vMR=v+u
vRaftR=u

In 1 hr, dist. covered by M = v+u km
In 1 hr, dist. covered by Raft = u km
Extra distance covered by motorboat = v km

let after time t they meet,
ut=t(v-u)
or 2u = v [since VMR when going upstream is -(v-u) (considering initial dirn positive]

Now, u(t+1) = 6 or ut + u = 6(1)
and (v+u) - (v-u)t = 6
or 3u - ut = 6 - (2)

Adding 1 and 2
4u = 12 or u = 3

Your Answer

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Asked by
Himanshu Giria

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