Date | November 2016 | Marks available | 2 | Reference code | 16N.2.SL.TZ0.6 |
Level | Standard level | Paper | Paper 2 | Time zone | 0 - no time zone |
Command term | Define and State | Question number | 6 | Adapted from | N/A |
Question
(i) Define gravitational field strength.
(ii) State the SI unit for gravitational field strength.
A planet orbits the Sun in a circular orbit with orbital period T and orbital radius R. The mass of the Sun is M.
(i) Show that .
(ii) The Earth’s orbit around the Sun is almost circular with radius 1.5×1011 m. Estimate the mass of the Sun.
Markscheme
(i) «gravitational» force per unit mass on a «small or test» mass
(ii) N kg–1
Award mark if N kg-1 is seen, treating any further work as neutral.
Do not accept bald m s–2
i
clear evidence that v in is equated to orbital speed
OR
clear evidence that centripetal force is equated to gravitational force
OR
clear evidence that a in etc is equated to g in with consistent use of symbols
Minimum is a statement that is the orbital speed which is then used in
Minimum is Fc = Fg ignore any signs.
Minimum is g = a.
substitutes and re-arranges to obtain result
Allow any legitimate method not identified here.
Do not allow spurious methods involving equations of shm etc
ii
«T = 365 × 24 × 60 × 60 = 3.15 × 107 s»
2×1030«kg»
Allow use of 3.16 x 107 s for year length (quoted elsewhere in paper).
Condone error in power of ten in MP1.
Award [1 max] if incorrect time used (24 h is sometimes seen, leading to 2.66 x 1035 kg).
Units are not required, but if not given assume kg and mark POT accordingly if power wrong.
Award [2] for a bald correct answer.
No sf penalty here.