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

t=320s

Step-by-step 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)=(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)=(3000m)/(25m/s)\\ t_(2)=120m/s`

Now the total time

`t=t_(1)+t_(2)\\t=(200+120)s\\t=320s`