#### Transcript of 8. Gravitational Field Summary

photo credit Nasa / Goddard Space Flight Center / Reto Stöckli

Gravtational Force

NEWTON's LAW of GRAVITATION

Gravitational Field Strength

gravitational force per UNIT MASS

of object with mass M

Gravitational Potential

Work Done in moving UNIT MASS from infinity to final point (radius R away from centre of body of mass M)

Gravitational

Potential Energy

Work done required in moving body of mass m from infinity to final position (radius R away from centre of body of mass M)

Escape Velocity

minimum kinetic energy required for gain in GPE from surface to Earth to INFINITY

GRAVITATIONAL FIELD

summary

gravitational constant

Earth: g = 9.81 N/kg

gravitational field lines

gravitational potential at infinity = ZERO

Equipotential Surface

mrcheung

Satellites in Circular Orbits

Gravitational Force = Centripetal Force

**GRAVITATIONAL FIELD**

minimum starting velocity

loss in KE = gain in GPE

i.e. Earth surface - only KE -->

infinity - only GPE, no KE

Geostationary Orbit

Period of revolution, T = 24 hours

plane of revolution in plane with Equator

satellite revolves from WEST to EAST

Energy of Satellite in Orbit

**U**

**g**

gravitational field strength

gravitational force

gravitational potential energy

gravitational potential

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