Three identical point masses

PHYSICS · Single correct · AP · Physics C: Mechanics · Energy and Momentum of Rotating Systems · Energy and Momentum of Rotating Systems

Problem

Three identical point masses, each of mass

0.50\,\text{kg}

, are fixed at the coordinates

(0,0)

(0.40\,\text{m},0)

, and

(0,0.40\,\text{m})

in the

xy

-plane. At a particular instant their velocities are

\mathbf v_{1}=2.0\,\hat\imath\,\text{m\,s}^{-1}

\mathbf v_{2}=2.0\,\hat\imath+3.0\,\hat\jmath\,\text{m\,s}^{-1}

, and

\mathbf v_{3}=3.0\,\hat\jmath\,\text{m\,s}^{-1}

, respectively. What is the rotational kinetic energy of the system about its center of mass at that instant? (a)

6.5\,\text{J}

(b)

2.2\,\text{J}

(c)

3.0\,\text{J}

(d)

4.3\,\text{J}