On Sun, 25 Jul 1999 19:02:13 -0400 "Michael S. Lorrey" <email@example.com> writes:
The gravitational attraction is only important if sailmass X gravitationalacceleration > solarwindmass X windvelocity^2. The lighter the mass of your sail versus the area, the better.
Mass X acceleration equates to units of force, but mass X velocity^2 equates to units of energy. Since 'impulse', which is force X time, equates to momentum, which is mass X velocity, force equates to [mass X velocity] / time.
So, would it not be more correct to express the inequality as
sailmass X gravitationalacceleration > [solarwindmass / time] X windvelocity,
so that the units balance?
In other words, if mass is impacting a target at the rate of one kilogram per second with a relative velocity of one meter per second, and if the collision is non-elastic such that all the momentum of the impacting mass (relative to the target) is transferred to the target, the force imparted to the target is one Newton.