- #1

charbon

- 23

- 0

## Homework Statement

a disc of radius r spins uniformly around its axis at an angular velocity [tex]\omega[/tex] in a clockwise motion. the center moves on the horizontal line z = r of a vertical axis Oxz of the referential Oxyz. We call R' = Cxyz, in translation compared to R= Oxyz, of origin C and we specify [tex]\theta[/tex] the angle made by a CA from the disc with Cz, A being a point of the perimeter of the disc.

a) express in R, the velocity and acceleration of A compared to R'

b) What velocity, in R, must we give to C in order for the velocity [tex]\vec{vb}[/tex]/R of the lowest point of the disc be 0?

## Homework Equations

I am having a hard time finding b)

first off, I wrote the velocity-addition formula

[tex]\vec{vb}[/tex] = [tex]\vec{vb'}[/tex] + [tex]\vec{V}[/tex]

thus

[tex]\vec{V}[/tex] = [tex]\vec{vb}[/tex] - [tex]\vec{vb'}[/tex]

but [tex]\vec{vb}[/tex] = 0

so

[tex]\vec{V}[/tex] = - [tex]\vec{vb'}[/tex]

This is where I am stuck. How do I find this vector?