 |
| Summary |
|
- The centre of mass is an imaginary point where one can assume the entire mass of the given system or object to be positioned.
|
| |
- Principle of conservation of linear momentum states that the linear momentum of a system remains constant if the external forces acting on the system add up to zero.
|
| |
- If no external force acts on a two particle system and its centre of mass is at rest initially, it remains fixed even when the particles individually move and accelerate.
|
| |
- The position of the centre of mass of a rigid body depends on:
|
| |
| (i) Shape of the body |
| |
| (ii) Distribution of mass in the body |
| |
- For rigid bodies of regular geometrical shapes and having uniform distribution of mass, the centre of mass is at their geometrical centres.
|
| |
- Angular velocity of a rotating rigid body is the rate of change of angle swept.
|
| |
- Torque is the product of the magnitude of the force and the lever arm of the force.
|
| |
- To increase the turning effect of force, it is not necessary to increase the magnitude of the force itself.
|
| |
- If the total external torque on the system is zero, its angular momentum remains constant. This is known as the principle of conservation of angular momentum.
|
| |
- If angular momentum remains constant, areal velocity should also remain constant. Kepler's second law states that area swept by the radius vector of the planet in equal intervals of time is same, or in other words, areal velocity of the planet is constant.
|
| |
- The moment of inertia of a body about an axis is equal to its moment of inertia about a parallel axis through its centre of gravity plus the product of the mass of the body and the square of the perpendicular distance between the two parallel axes.
|
| |
- The moment of inertia of a plane lamina about an axis perpendicular to its plane is equal to the sum of the moments of inertia of the lamina about any two mutually perpendicular axes, passing in its own plane, intersecting each other at the point through which the perpendicular axis passes.
|
| |
