Definition of gravitational field and field strength:

• Gravitational field is a region in which the mass of an object experiences a force due to gravitational attraction.


• Gravitational field strength, g, is defined as gravitational force per unit mass.


• Any object placed around the Earth experiences a force pulling it towards the Earth. So, the earth is surrounded by a gravitational field. The force is strongest on the surface of the Earth and gets weaker as we go further away.
  
  

  

• There is gravitational field around the Earth. A gravitational field is the region within which a mass experiences a force of attraction.


• On the earth's surface, the gravitational field strength g is approximately 10N kg-1.


• The gravitational force on:

1) 1kg mass is 10N

2) 2kg mass is 20N.

3) 3kg mass is 30N.

4) m kg mass is mg.

• The gravitational force on a mass is known as its weight. Hence, the weight of a mass m is given by:
  

Weight = mass x gravitational field strength = mg .

• The gravitational field strength of the Earth decreases as the altitude increases.


• On the surface of the Moon, the gravitational field strength is about 1/6 the value of g on the Earth surface.


• Hence, the weight ( w = mg ) of an object is not constant but changes when the value of g changes.


• From the equation, Force = mass x acceleration, an object, of mass m experiences a gravitational force of F, which is equal to mg. Hence, mg = mass x acceleration.


• Acceleration of object on the earth's surface = weight / mass = mg / m = g = 10ms-2.


• The acceleration of an object that falls freelt under the action of gravitational force is known as the acceleration due to gravity.


• On the earth's surface, g = 10ms-2.

G-R-A-V-I-T-Y.

Demonstration of gravity:

Life without gravity ?