Question is...even if it hit Earth...how much of it would be burned up on entry? Would it hit Earth at say a 20 story building versus a 25 story building?
lol... like that would matter...
Earth’s atmosphere gives protection against the vast majority of small asteroids which hit. Asteroids hit the atmosphere at typical speeds in excess of 10 km/sec — an average of about 20 km/sec for asteroids whose entire orbits reside within the inner solar system, with exact relative speed depending upon their angle of approach, and with speeds over 50 km/sec common for small cometary objects making a pass from the outer solar system. At this speed, they usually break up due to severe shock pressures, and burn up due to friction with the atmosphere. Think about it — 10 kilometers per second (6 miles per second) is awfully fast — about 36,000 kilometers (22,000 miles) per hour.
For asteroids coming in at 20 km/sec, it’s generally thought that to penetrate the atmosphere and cause major damage by tsunami, an iron asteroid must be around 40 to 60 meters in diameter, and a stony asteroid 200 meters in diameter (Hills, 1994, paper ref.). However, a stony asteroid 60 meters in diameter can cause significant damage by airbursts (Hills and Goda, 1993, paper ref.).
http://www.permanent.com/a-impact.htm