Physics > Rotational Dynamics > 5.0 Rotational kinetic energy
Rotational Dynamics
1.0 Introduction
1.1 Torque or moment of a force
1.2 Relation between torque and moment of inertia
1.3 Pseudo torque
1.4 Torque equation
1.5 Principal of moments
2.0 Angular momentum or moment of a momentum
3.0 Relation between torque and angular momentum
4.0 Combined translational and rotational motion of a rigid body
5.0 Rotational kinetic energy
6.0 Uniform pure rolling
7.0 Accelerated pure rolling
8.0 Instantaneous axis of rotation
9.0 Toppling
5.1 Total kinetic energy of a rigid body in a combined translational and rotational motion
1.2 Relation between torque and moment of inertia
1.3 Pseudo torque
1.4 Torque equation
1.5 Principal of moments
In combined translation and rotational motion, the total kinetic energy $(K)$ of a rigid body is sum of the translational kinetic energy $\left( {{K_T}} \right)$ and the rotational kinetic energy $\left( {{K_R}} \right)$ $$\begin{equation} \begin{aligned} K = {K_T} + {K_R} \\ K = \frac{1}{2}mv_{com}^2 + \frac{1}{2}I{\omega ^2} \\\end{aligned} \end{equation} $$
where,
${v_{com}}$: Velocity of centre of mass
${I_{com}}$: Moment of inertia about an axis of rotation
$\omega $: Angular velocity about an axis of rotation
In the above case the axis of rotation is at the centre of mass. Therefore, $$K = \frac{1}{2}mv_{com}^2 + \frac{1}{2}{I_{com}}{\omega ^2}$$