Question 932058
The time it takes for an object to hit the ground under gravity's influence is,
{{{2R=(1/2)gt^2}}}
{{{(4R)/g=t^2}}}
{{{t=(4R)/g}}}
The time it takes for the ferris wheel to make (1/2) a revolution is equal to 
One revolution is {{{2pi}}} radians.
Half a revolution is {{{pi}}} radians.
If the ferris wheel travels at {{{W}}}{{{rad/s}}}.
Then,
{{{t=W/pi}}}
So then set these equal to each other.
{{{W/pi=(4R)/g}}}
{{{W=(4*pi*R)/g}}}
Using your radius,
{{{W=(4*pi*5)/9.8=6.4}}}{{{rad/s}}}
which convert to about 61 RPM or about 1 revolution per second.
That's pretty fast for a 5M wheel to rotate.
Amusement park rides like the Rotor spin at about 20-30 rpm for reference.
Ferris wheels are on the order of 1-2 rpm.