Melody

Hi Alan and Badinage  

So Badinage, if there is a 'whole raft of solutions' are you going to give us one of them that Alan won't poke holes in ?  LOL

59.8=16.2*t+4.9t^2

rearrange

4.9t^2+16.2t-59.8=0

now solve it useing the quadratic formula.

y+3-(7+y)=-4

I look at the left hand side

y+3-(7+y)

= y+3-1(7+y)

=y+3 -1*7+-1*y

=y+3-7-y

=3-7

=-4

=right hand side  aways!

So y can be absolutely any number and this statement will always be true!

Thanks Alan, 

I will take a little time to absorb this.

this      dA= 2pi L dR     was a typo,  I did mean dr       

the rest i will need to think about.    

Thanks MG.

Do you actually look at the posts that I include?  

I always wonder how many people really look at what I write :/

I know many members like to see their names included.  

It is always nice to see some recognition when we put effort into something.  :)

There are not any rational numbers that will do this.

What! not me, what did I spell wrong?  LOL   

Thanks Alan and 7up,

I am trying to work out the first bit of this in terms of the mathematics.

I understand what 7up said.

I think I can see that a shell  has the volume of    dA= 2pi L dR       Is that right?

I can see that    $$R=\int dR$$

From what 7up said it seems logical that Resistance is inversely proportional to volume as the radius increases.

and i am guessing that $$\rho$$    is a contant for the specific material that the cylinder is made from.

So    

 $$\\R(of a shell)=dR=\frac{\rho}{dA}=\frac{\rho}{2\pi r L}\;dr\\\\
R=\int dR=\int_a^b\frac{\rho}{A}\;dr=\int_a^b\;\frac{\rho}{2\pi r L}\;dr\\\\$$

Is what I have written correct?  I am confused :/  

10 down (bang1)

5 up

5down (2)

2.5 up

2.5 down (3)

1.25 up

1.25 down (4)

Now add them up :)

Thanks,  

There is no reason that she would be blocked :)