A man points his boat due east and rows at 4 km h^-1 relative to the water. The river flows south at 2 km h^-1, and it is 1 km wide.
a) How fast is the man moving relative to the shore?
b) Where will he land?
c) How long will his trip take?

Please help, I have no idea how to do this, thanks

Question

A man points his boat due east and rows at 4 km h^-1 relative to the water. The river flows south at 2 km h^-1, and it is 1 km wide. 
a) How fast is the man moving relative to the shore?
b) Where will he land?
c) How long will his trip take?

Please help, I have no idea how to do this, thanks

badhi · Answer

relative to the water his movement is 4 to the east... but the water is flowing to the south.. according to the relative velocity identity,

$V(b,s) = V(b,w)+V(w,s)$

b is boat, s is shore and w is water. V(b,s) is velocity of the boat relative to the shore. other expressions have the similar meaning

|dw:1442463193079:dw|

you can find the resultant velocity with the vector addition and it will be equal to $V(b,s)$

anonymous · Answer

How do I find out where he will land?

anonymous · Answer

And the time as well? I'm still a bit confused

badhi · Answer

now that you know his velocity with reference to the ground, its jst a matter of using motion equations...

|dw:1442463807902:dw|

from $V(b,s)$ you know the value of $\theta$ so find the value of x,and the distance he will land ,

since you know x and v(b,s) you can find the time taken to travel