Читать книгу Fundamentals of Heat Engines - Jamil Ghojel - Страница 24

The angular momentum of body about an axis is the moment of its linear momentum about the axis. Figure 1.5 shows a body rotating with angular velocity ω about an axis passing through 0 (perpendicular to the plane of the page):

 Linear momentum of particle of mass dm = dm ωl

 Moment of momentum of particle about 0 = dm ωl2

 Total momentum H0 of the body about 0 for constant angular velocity(1.18)

If G is the centre of gravity of the body,

(1.19)

and the angular momentum of the body can be written as

(1.20)

Figure 1.5 Angular momentum of a rigid body.

The angular momentum of a rigid body about any axis remains constant, unless an external torque about the same axis is applied. This is known as the law of conservation of angular momentum.