# 29.1 Kinetic Energy of Rotation | Summary and Q&A

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June 2, 2017
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29.1 Kinetic Energy of Rotation

## TL;DR

This content discusses the kinetic energy of rotation and the concept of moment of inertia in rigid bodies.

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### Q: How is the angular velocity of a rigid body described?

The angular velocity of a rigid body is described as the rate at which the angle is changing with respect to the axis of rotation, represented by the vector omega.

### Q: What is the relationship between the tangential velocity and the angular velocity of a mass element in a rotating rigid body?

The tangential velocity of a mass element in a rotating rigid body is given by v = r * omega_z, where r is the distance from the center and omega_z is the z-component of the angular velocity.

### Q: How is the rotational kinetic energy of a rigid body calculated?

The rotational kinetic energy of a rigid body is calculated by summing up the rotational kinetic energy of each mass element, which is given by 1/2 * delta m * r^2 * omega_z^2, where delta m is the mass element, r is the distance from the center, and omega_z is the z-component of the angular velocity.

### Q: What is the moment of inertia of a continuous body?

The moment of inertia of a continuous body about an axis passing through a point is defined as the integral over the body of a small mass element dm multiplied by the square of the distance r from the axis to the mass element. It measures the body's resistance to rotation around that axis.

## Summary & Key Takeaways

• The content introduces the concept of a rigid body rotating about an axis and describes the coordinate system used to analyze it.

• It explains the relationship between the angular velocity and the tangential velocity of a mass element in the rigid body.

• The content then explores the rotational kinetic energy and introduces the moment of inertia as a measure of an object's resistance to rotation.