In Robert Helnlein's The Moon Is a Harsh Mistress, the colonial inhabitants of the Moon threaten to launch rocks clown onto Earth if they are not given independence (or at least representation). Assuming a gun could launch a rock of mass m at 2.50 times the lunar escape speed, calculate the speed of the rock as it enters Earth's atmosphere. (We interpret "lunar escape speed" to be the escape speed from the surface of a stationary Moon alone in the universe.) [ lkm/s Need Help? m