A ferry boat is crossing a river that is 8.5 x 10^2 m wide.

[Ayushi]

Homework Statement

A ferry boat is crossing a river that is 8.5 x 10^2 m wide.

The average velocity of the water relative to the shore is 3.8 m/s E and the average velocity of the boat relative to the water is 4.9 m/s S.
How long does it take for the boat to get across?

Homework Equations

The Attempt at a Solution

The velocity of the boat relative to the shore is 6.2 m/s [52° E of S].

 

[BvU]

Hello ayushi,

The velocity of the boat relative to the shore is 6.2 m/s [52° E of S].

How did you come to that conclusion ?

 

[Ayushi]

Hello ayushi,

How did you come to that conclusion ?

I used the pythagorean theorem to figure the velocity of the boat relative to the shore.
3.8 m/s E ^2 + 4.9 m/s S ^2
And got 6.2 m/s E of S

 

[RPinPA]

Think of it from the point of view of the boat. How fast is the shore approaching if the boat is pointed straight across the river?

You'll also need the distance to the other shore, which I assume you were given even though you didn't include it.

 

[jbriggs444]

I used the pythagorean theorem to figure the velocity of the boat relative to the shore.
3.8 m/s E ^2 + 4.9 m/s S ^2
And got 6.2 m/s E of S

6.2 meters per second yes. But the angle is suspect.

You'll also need the distance to the other shore, which I assume you were given even though you didn't include it.

It is stashed in the title -- 850 meters.

 

[gneill]

The problem statement does not specifically indicate whether the ferry is to land directly opposite its starting point, or just reach the other shore in the quickest time possible (although this is a common enough problem type that it is almost surely the former case). Just thought I'd point that out. Imprecisely stated problem statements can sometimes be time wasting as helpers have to tease out the details before being able to work the actual problem.