Angular momentum merry go round

[sumitmanhas]

Homework Statement

Suppose a 74 kg person stands at the edge of a 6.6 m diameter merry-go-round turntable that is mounted on frictionless bearings and has a moment of inertia of 1820 kg.m^2. The turntable is at rest initially, but when the person begins running at a speed of 4.1 m/s (with respect to the turntable) around its edge, the turntable begins to rotate in the opposite direction.
Part A
Calculate the magnitude of the angular velocity of the turntable.

Homework Equations

conservation of angular momentum

The Attempt at a Solution

this is how i approached it.
initial angular momentum = 0
final anglar momentum = I(\omega_P) - I(\omega_T)

while \omega_p = v/r and I_P = MR²

MR²V/R - I(\omega_T) = 0

\omega_T = MRV/I_T

\omega_T = (74)(3.3)(4.1)/ 1820

\omega_T = 0.55 RAD/S

but due to some reason turns out to be the wrong answer , someone please help ??

 

[Doc Al]

The speed of the person is given with respect to the turntable, not with respect to the ground (which is what you need).

Hint: If the angular speed of the turntable (with respect to the ground) is ω, what would be the angular speed of the runner with respect to the ground?

 

[sumitmanhas]

what i think is that angular velocity of the person with respect to ground = 4.1 + angular velocity of table
can be wrong though...someone reply as soon as possible this question is due within an hour

 

[Doc Al]

what i think is that angular velocity of the person with respect to ground = 4.1 + angular velocity of table
can be wrong though...someone reply as soon as possible this question is due within an hour

Almost. But 4.1 m/s is a linear speed, not an angular velocity. Convert it to an angular velocity first.

 

[sumitmanhas]

but what would be the angular velocity of the turntable then for finding the angular velocity of the person with respect to ground . do i use then one i calculated at my first attempt . and then plug it into equation for finding the angular velocity of person with respect to ground.??

and then after finding the angular velocity of the person with respect to ground u plug it back into the very first equation for finding angular velocity of the table.
tried this whole thing but never worked.

help ??