# Rolling Disk of Spruce and Steel#

A disk that will appear to roll uphill is made from spruce ($$\rho\_{\text{spruce}} =$$ 472.0 $$kg/m^3$$) and steel ($$\rho\_{\text{steel}} =$$ 7840.0 $$kg/m^3$$) by drilling a 3 $$cm$$ diameter hole, centred 8 $$cm$$ above the centre of a 30 $$cm$$ diameter spruce cylinder, as shown in the figure. Into this hole is inserted a piece of steel of identical dimensions. The disk has a thickness of 27.7 $$cm$$.

## Part 1#

Calculate the mass of the spruce removed from this disk.

Please enter in a numeric value in $$kg$$.

## Part 2#

Calculate the mass of the steel that replaces the spruce.

Please enter in a numeric value in $$kg$$.

## Part 3#

The location of the centre of mass of the weighted disk is closest to:

• $$x$$ = 1 $$cm$$, $$y$$ = 0 $$cm$$

• $$x$$ = 0 $$cm$$, $$y$$ = 1.0 $$cm$$

• $$x$$ = 0 $$cm$$, $$y$$ = 2.0 $$cm$$

• $$x$$ = 0 $$cm$$, $$y$$ = 3.0 $$cm$$

• $$x$$ = 0 $$cm$$, $$y$$ = 4.0 $$cm$$

• $$x$$ = 0 $$cm$$, $$y$$ = 0.0 $$cm$$