Relative Velocity and Vector Resolution

[Jacobpm64]

You row a boat perpendicular to the shore of a river that flows at 3.0 m/s. The velocity of your boat is 4.0 m/s relative to the water.
a. What is your velocity of your boat relative to the shore?
b. What is the component of your velocity parallel to the shore? Perpendicular to it?
A was very easy... If you draw it out, you can easily see that it's a 3,4,5 triangle, so the answer to A is 5 m/s.
I'm not sure how to work out B. Which number do I use to find the components? Would the parallel to the shore component be 4 m/s? Would the perpendicular be 3 m/s? I'm not sure.. Or is it totally different numbers? Help with part B please.

 

[Doc Al]

You can use the same triangle that you drew for A to work out the components for B. It's easier than you think.

 

[Jacobpm64]

ok, which sides am i using of the triangle? it's a 3,4,5 triangle. Am i correct in saying that the velocity component parallel to the shore is the velocity of the river (+3 m/s --- since it is flowing parallel to the shore) and the velocity component perpendicular to the shore is the velocity of the boat relative to the river (+4 m/s --- since the boat is moving in a direction perpendicular to the shore)?

 

[Doc Al]

Sounds good to me.

 

[Jacobpm64]

thanks a lot