Applied maths - Relative Velocity

Incompetent

Well really this question goes for all of applied maths, but how do I go about learning relative velocity? I'm trying to work through exam papers with my book but I can't get it. I've gotten Vab= Va - Vb, and I can work the relative velocity out (sometimes), but I don't know how to get the direction (relative direction). Anyone help?
I'm doing a revision course for this soon, and I really need to brush up on the basics!

MegGustaa

Incompetent wrote: »

Well really this question goes for all of applied maths, but how do I go about learning relative velocity? I'm trying to work through exam papers with my book but I can't get it. I've gotten Vab= Va - Vb, and I can work the relative velocity out (sometimes), but I don't know how to get the direction (relative direction). Anyone help?
I'm doing a revision course for this soon, and I really need to brush up on the basics!

You get the direction by plotting the relative velocity on the i-j plane. By getting the Tan of the angle it makes with the x-axis, you can find the angle. Then you put that in the form 'E(angle)N' or '(angle)North of East' (or whichever directions apply!)

acorn1702

Which book are you using? My applied maths teacher has beef with chapter four of the fundamental applied maths book because the chapter is called relative velocity but a lot of it is infact resultant velocity.

For Relative/apparent wind questions split the question into two events: you will get an equation in xi and yj for event one and another equation for event two. Then it's just a simultaneous equation to solve. Remember to always convert your i and j vectors into magnitude and direction.

I found closest approach questions difficult at first and couldn't explain on them here, what county are you in? It would be definitely worth getting a grind or two on question two in particular.

Stalin and rugby

Relative velocity is a bitch, takes forever to understand I don't blame you. If possible leave it out. I found it to be the trickiest and most time consuming out of the lot

You still have many other options you don't HAVE to do it

(P.S this is advice coming from a guy who failed his applied maths mock )

Wesc.

You should learn relative velocity well... it came up in a Collisions question in 2002 I think!

The book I used to teach myself relative velocity is Applied Mathematics by Dominick Donnelly, you can only buy it online as far as I know. In my opinion Oliver Murphy's Fundamental Applied Mathematics is a heap of ****e :P

ride-the-spiral

I used Murhpy's book to teach myself last year, I thought it was quite good when I was doing the Leaving, but having done a year of 3rd level mechanics I think there are some topics which could be explained better.