Linking questions:

• What measurements of a binary star system need to be made in order to determine the nature of the two stars? 

• How is uniform circular motion like—and unlike—real-life orbits?

• How is the amount of fuel required to launch rockets into space determined by considering energy? 

• How can air resistance be used to alter the motion of a satellite orbiting Earth? 

• What are the benefits of using consistent terminology to describe different types of fields? (NOS)

• How can the motion of electrons in the atom be modelled on planetary motion and in what ways does this model fail? (NOS)

• Physics utilizes a number of constants such as G. What is the purpose of these constants and how are they determined? (NOS)

Understandings: 

• Kepler’s three laws of orbital motion 

• Newton's universal law of gravitation for bodies treated as point masses 

• conditions under which extended bodies can be treated as point masses 

• that gravitational field strength g at a point is the force per unit mass experienced by a small point mass at that point

• gravitational field lines.

• that the gravitational potential energy Ep of a system is the work done to assemble the system from infinite separation of the components of the system 

• the gravitational potential energy for a two-body system as given by Ep = –G Mm/r where r is the separation between the centre of mass of the two bodies 

• that the gravitational potential Vg at a point is the work done per unit mass in bringing a mass from infinity to that point as given by V = –GM/r

• the gravitational field strength g as the gravitational potential gradient as given by g = – ΔVg/Δr 

• the work done in moving a mass m in a gravitational field as given by W = mΔVg 

• equipotential surfaces for gravitational fields 

• the relationship between equipotential surfaces and gravitational field lines 

• the escape speed at any point in a gravitational field

• the orbital speed of a body orbiting a large mass 

• the qualitative effect of a small viscous drag force due to the atmosphere on the height and speed of an orbiting body.

Simulations:

Phet - Kepler's Laws

Files to support your learning:

Presentation - Unit D1 Fields

Resource - Gravitational fields worksheet

Resource - Orbital motion questions

Resource - Unit D1 review sheet

Support - fields question set 

Support - fields question set markscheme

Support - gravitational fields questions

Support - gravitational fields questions markscheme

Support - Gravitational fields questions worked examples

Support - GPE and potential