# KS5 Gravitational Fields

**Gravitational ****Learning Objectives**

**Learning Objectives**

**Content**

- Concept of a force field as a region in which a body experiences a non-contact force.
- Students should recognise that a force field can be represented as a vector, the direction of which must be determined by inspection.
- Force fields arise from the interaction of mass, of static charge, and between moving charges.
- Gravity as a universal attractive force acting between all matter.
- Magnitude of force between point masses: F = Gm
_{1}m_{2}/r^{2 }where G is the gravitational constant. - Representation of a gravitational field by gravitational field lines.
- g as force per unit mass as defined by g = F/m
- Magnitude of g in a radial field given by g = GM/r
^{2} - Understanding of definition of gravitational potential, including zero value at infinity.
- Understanding of gravitational potential difference.
- Work done in moving mass m given by ∆W = m∆V
- Equipotential surfaces.
- Idea that no work is done when moving along an equipotential surface.
- V in a radial field given by V = − GM/r
- Significance of the negative sign.
- Graphical representations of variations of g and V with r.
- V related to g by: g = − ∆ V/∆ r
- ∆ V from area under graph of g against r.
- Orbital period and speed related to radius of circular orbit; derivation of T
^{2}∝ r^{3} - Energy considerations for an orbiting satellite.
- Total energy of an orbiting satellite.
- Escape velocity.
- Synchronous orbits.
- Use of satellites in low orbits and geostationary orbits, to include plane and radius of geostationary orbit.