## Wednesday, May 7, 2008

### Concept Review - Chapter 11 Gravitation

Universal law of gravitation

F = GMm/r²

Universal constant of gravitation (G)

G = 6.67*10^-11 N-m² /kg²

Gravitational potential energy

Gravitational potential

Gravitational potential at a point is equal to the change in potential energy per unit mass, as the mass is brought from the reference point to the given point.

Gravitational field

It is assumed that a body say A, creates a gravitational field in the space around it. The field has its own existence and has energy and momentum. When another body B is placed in gravitational field of a body, this field exerts a force on it. The direction and intensity of the field is defined in terms of the force it exerts on a body placed in it.

The intensity of gravitational field vector E at a point is defined by the equation

vector E = force vector F/mass

where F is the force vector exerted by the field on a body of mass m placed in the field. The intensity of gravitational field is abbreviated as gravitational field. Its SI unit is N/kg.

By the way they are defined, intensity of gravitational field and acceleration due to gravity have equal magnitudes and directions, but they are two separate physical quantities.

Acceleration due to gravity (g)

Variation in the value of g

Kepler's laws

Time period of a planet

Escape velocity

gravitational binding energy

Black holes

Inertial and gravitational mass

Geostationery satellite