Oh and I'm using the definition that .
Let , where and is the unit vector aligned to the vertical direction. We need to show that is proportional to the horizontal part of .
I'm guessing that , and using we get .
But then when we "dot" u and we get 0?
Am I missing something here, this doesn't seem to make sense?
Thanks in advance for the help.
Thanks for the reply!
But then surly when you combine this with the outside of the brackets you get the zero vector?
Sorry if I'm missing something obvious.
Ahh of course because the dot product produces a scalar, which you have to then 'multiply' each term in the vector by!
So working this out I get .
I think this ok, but how do we know exactly that it's proportional to the horizontal part of ? Is it because the value for is zero?
Thanks again for the reply, really helped.
Now why couldn't I come up with that a second ago!!!
Thankyou again for all your help with this.
(PS I hope what I've just said is actually correct?)