One question about comets or/and asstroids?

Question

what if a comet hits china and we live at north america how many seconds or mintunes will it take to reach north america and how do you survive it?

Answer 1

Don't worry about it.  If an asteroid is going to hit the Earth, we'll know well in advance, and everything you'll need to know will be disseminated. :)

Answer 2

if a comet is about to hit the earth, we earthlings will be prepared for it well in advance, to disintegrate the comet/asteroid into bits. If it hits china, nothing is ought to happen in America and the vice versa.

If you think that shock waves will travel to America, that is possible only if the comet is really large - larger than any known ones. if that is to happen, it will depend on at what pace the comet hit us. the faster the pace, the faster the shock waves reaches America, (through the diameter of the earth).

Answer 3

You can use the Impact effects calculator. Let's say, you are 10000 km away from the impact and the impactor is a very massive and fast comet, like Hale-Bopp, with 70 km diameter:

You would first notice the impact one hour later, as a magnitude 11.8 on the Richter scale earthquake, but because of the large distance, you will only feel some shaking in the USA.

Only a harmless warning of what will arrive 14 hours later: A hurricane strength blast wave toppling trees and damaging houses.

In China, a 700 km crater with 2 km depth will form.

Luckily, such a impact was so far only happening in the early history of Earth and is very unlikely in the future.

You can calculate the effects of less powerful impacts, but unless it is also on the "planet killer" scale, like my example, the effects you feel in the USA are mostly harmless.