•Chandrasekhar’s (1960) formula:
•dv/dt = -(v/v3)16π2(ln Λ)G2m(m+M)∫f(v)v2dv
•where Λ is a factor of order 1 involving the masses, impact parameter
and initial velocity, f is the stellar density, M is the
intruder, m is the stellar mass.
•If the intruder
is mass, M >> m, then
•dv/dt ~ -v 16π2(ln Λ)G2mM f(0)
•So the force
proportional to velocity in this case, a viscous
friction. Concerned with the mass
density of stars, not individual masses. Force dependent on M, intruder
mass. The FORCE goes as mass
squared.