Question

A boat is able to move throught still water at 20m/s. It makes a round trip to a town 3.0km upstrea. If the river flows at 5m/s, the time required for this round trip is

Answer 1

Answer:

t=320s

Explanation:

Given Data

Boat speed=20 m/s

River flows=5 m/s

Total trip of distance d=3.0km = 3000m

To find

Total time taken

Solution

As

$Velocity=distance/time\\time=distance/velocity$

Here we have two conditions

First when boat moves upward and the river pushing back.then velocity is given as

velocity=20m/s-5m/s

velocity=15 m/s

Time for that velocity

$t_{1} =distance/velocity\\t_{1}=\frac{3000m}{15m/s}\\ t_{1}=200s$

Now for second condition when river flows and boat speed on same direction

velocity=20m/s+5m/s

velocity=25 m/s

Time taken for that velocity

$t_{2}=distance/velocity\\t_{2}=\frac{3000m}{25m/s}\\ t_{2}=120m/s$

Now the total time

$t=t_{1}+t_{2}\\t=(200+120)s\\t=320s$