Answer Happy

QUESTION 2. (2a) It is a reasonable assumption that the force of dynamical friction depends only on the mass m of the object experiencing the friction, its velocity Vm, and the density p of the medium through which it is moving: fp = C(Gm)"V hp with C being a dimensionless constant. Use this relation to derive an expression for the force of dynamical friction (determine the values of a, b and c). [6 marks] (2b) Show that this relation becomes fp =CGm²/47rif we are considering an object located in a region far from the centre of a spiral galaxy, where the galactic rotation curve is flat. [8 marks] (2c) By considering the torque exerted on the object by the force of dynamical friction, show that the time scale for the object to spiral from an initial radius ri into the centre of the galaxy due to the action of dynamical friction is the following: (12 marks] At 2πυγη? CGm