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Nugatory
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#6
Dec11-12, 09:53 PM
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Quote Quote by davenn View Post
I would consider that the difference in size of say an asteroid up to ~ 1km across compared to the size of the earth, the gravitational PE may not be a large factor compared to the KE of the incoming asteroid.
average incoming velocity of a meteor/asteroid ..... 30 - 40 km / sec
acceleration due to gravity 9.81m/s2 .... big difference, orders of magnitude
But look at the units... The acceleration is measured in meters per second per second, meaning that every second the speed increases by 9.8 meters/sec.... Let that go for a few hundred seconds and you've built up some serious speed. (note: gravitational acceleration is only 9.8 m/sec at the surface of the earth; it declines steadily the further away from earth you are).

It turns out that an object falling from infinity to the surface of the earth will reach a speed of about 11 km/sec; that's its gravitational potential energy being converted into kinetic energy. It's a lot.