Assume a spherical rock. At r = 22.5’, V = 47,713 ft^cu, or about 1800 cu yds in round numbers.
Concrete density is around 2 tons per yard, so there is 3600 tons. So we’d need some rock significantly more dense that concrete.
By the way, I did the math on 10,000 tons at 40,000 mph, and that comes out to 346,000 tons of TNT worth of kinetic energy.
I just woke up and had yet another sci-fi recall, this book was about what happened when a super dense material hit earth, it was only the size of a baseball but weighed thousands of tons, it actually penetrated through the earth completely yet its exit was similar to a bullet exit and basically created a giant volcano.
Space could have anything from frozen mush comets to the afore mentioned super dense collapsed star material.
We could be hit with solid iron objects.
Makes for the intriguing discussion of what all the nations on earth could do....mine the asteroid field and to also create a defense net to divert these rogue objects.