GRAVITATIONAL

FIELD

By: Fadhilatus shoimah

• Gravitational force is not a contact force but a acting trough a distance in a space.

• Gravitational force is a space around an object with mass where other object, with mass in this space will experience the gravitational force.

• Earth gravitational field is an area around the earth which still influenced by the earth gravitational force.

• Gravitational field is including as vector quantity so that gravitational field can be visualized in the form of arrow. There arrows will show the magnitude and direction of gravitational fields at many points in the space and diagram of field lines / force lines.

• Gravitational field lines are the connected lines (continue) which always have direction toward the mass of gravitational field source.

• The closer distance between gravitational field lines produced by an object with a mass on a certain region, then the larger the gravitational field acting upon the other object with mass on that region.

• The quantity representing the gravitational field is called the gravitational field strength (gravitational force per unit of mass)

g =

• To calculate the gravitational field strength by source object with M in mass to the test object with M in mass at various point in gravitational field can be done by changing the value F in the equation above by the equation of gravitational force F = G , so that we obtain the following equation:

g = G / m =

• Where:

M = the mass of object source (kg) r = the distance of a point to the object source (m)

• The gravitational field strength of g is also called the gravitational acceleration. When an object with a mass m at rest or do not accelerated on the earth, so g is gravitational field strength. When an object with a mass m falls freely under the earth gravitational field influence, so g is earth gravitational acceleration.

• The values of g on the earth’s surface are rather various because this value depends on the location. So, the value of g at the poles is larger than at that of at the equator.

g =

• The farther the location of objects from the earth’s center, the smaller the gravitational acceleration at that location.

• The equation used to determine the value of g on the earth surface can also be used to determine the gravitational acceleration value g on other planet’s surface.

g =

• If we compare the gravitational acceleration of two planets, for example planet A with planet B, then we will obtain the comparison value as follows:

=

• Sample problem:1.) Earth mass 5,98 X kg and moon mass 7,35 X Radius earth moon m. Determine:a) Force that do by earth on moonb) Force that do by moon on earthc) Earth gravitational field strength on moond) Earth gravitational field strength on earth

• Solution:1.Given:

Mbumi = 5,98 x kgMbulan = 7,35 x Rbumi-bulan = 3,84 x m

Find:a) Force that do by earth on moonb) Force that do by moon on earthc) Earth gravitational field strength on moond) Earth gravitational field strength on earth

• Answer:

a) F = G

= 6,67x Nm²/kg = 1,99x N

b) Force that do by moon on earth is Force that do by earth on moon. So, 1,99x N

c) gbm-bl=G =6,67 x N/m²/kg² =2,7x N/kg

d) = G = 6,67x N/m²/kg² = 3,3x N/kg