Thank you thank you thank you! both of you have been very helpful, but these links are priceless ... just what I needed to be able to help him with his work. I can't tell you how grateful I am. Thanks again!
so, basically it's this formula:
velocity relative to x = velocity of a relative to x + velocity of b relative to x
except when you have velocities in opposite directions one of the values is negative. How do you decide which one is negative?
An example of the work he's trying to do is:
1. A stream's current has a velocity of 10 km/hr. You and a friend are trying to paddle upstream at 6 kn/hr. What is the resulting velocity.
2. My problem is that I cannot find the formula or equation that he needs to figure out the...