# Homework Help: Physics Force Problem Help

1. Oct 5, 2012

### asheik234

1. The problem statement, all variables and given/known data

A boat can travel a speed vB in still water. The boat needs to cross a river of width D from point A to point B on the opposite side directly across. On this particular day, the river's current has a speed of vR. Answer the following in terms of D, vB, and vR. For parts (a) and (b), the boat attempts crossing by pointing itself perpendicular to the river's current as shown.

(a) What is the angle θ?

(b) What is the component of the boat's velocity that is parallel to the dotted path?

2. Oct 5, 2012

### cybhunter

if your familiar with the real and imaginary plane system, it may look a little bit easier to handle.

There are two vectors, VB and VR (Vectors always contain a magnitude and a direction). The interaction of this two vectors will create a new vector dependent upon the angle difference and the magnitude. The key here is knowing what vector must VB be to cancel out the effects of VR

Hope this helps
Joe

3. Oct 6, 2012

### cheahchungyin

Assume that the boat does not resist any movement of current and follows the flow while still travelling towards the other side at its whole speed simultaneously.

angle= tan-1(Vr/Vb) <---this is the direction of the resultant velocity.

Component of boat's velocity will still be Vb.