Final answer:
To find the rotational kinetic energy of a platform, we need to calculate its moment of inertia and have the angular velocity. The formula involves these two values, but without the angular velocity provided, the rotational kinetic energy cannot be determined.
Step-by-step explanation:
The question asks for the rotational kinetic energy of a 119 kg horizontal platform that has the shape of a uniform disk with a given radius, rotating about a vertical axis through its center. To calculate the rotational kinetic energy (Erot), we use the formula: Erot = (1/2)*I*ω2, where I is the moment of inertia of the disk and ω (omega) is the angular velocity.
For a uniform disk, the moment of inertia (I) about an axis through its center is given by I = (1/2)*M*R2, where M is the mass of the disk and R is its radius. After calculating I, we need to know the angular velocity (ω) to find the rotational kinetic energy. However, the question does not provide ω, which is necessary to complete the calculation. Without ω, we cannot compute the rotational kinetic energy.
Once the angular velocity is known, the calculation would proceed by first finding I with the disk properties and then inserting ω and the computed I into the rotational kinetic energy formula.