Speed

http://twyfordigcsephysics.blogspot.co.uk/2012/09/speed.html

Quantities and units

http://twyfordigcsephysics.blogspot.co.uk/2012/09/units.html

http://twyfordigcsephysics.blogspot.co.uk/2012/09/quantities-and-units.html

space

http://twyfordigcsephysics.blogspot.co.uk/2013/07/space.html

orbital speed questions

http://twyfordigcsephysics.blogspot.co.uk/2013/07/answers-to-orbital-speeds-worksheet.html

Orbits

http://twyfordigcsephysics.blogspot.co.uk/2013/06/orbital-speeds.html

Gravity

http://twyfordigcsephysics.blogspot.co.uk/2013/06/gravity.html

mark scheme for the first part of the questions