the size of earth in km is 135 miles.
the size of earth in km is 135 miles.
what is the size of earth in km?
135 miles
Na
Na
the specific energy of an object such as a meteoroid falling on the earth from outside the earth's gravitational well is at least one half the square of the escape velocity of 11.2 km/s. this comes to 63 mj/kg (15 kcal/g, or 15 tonnes tnt equivalent per tonne). comets have even more energy, typically moving with respect to the sun, when in our vicinity, at about the square root of two times the speed of the earth. this comes to 42 km/s, or a specific energy of 882 mj/kg. the speed relative to the earth may be more or less, depending on direction. since the speed of the earth around the sun is about 30 km/s, a comet's speed relative to the earth can range from 12 to 72 km/s, the latter corresponding to 2592 mj/kg. if a comet with this speed fell to the earth it would gain another 63 mj/kg, yielding a total of 2655 mj/kg with a speed of 72.9 km/s. since the equator is moving at about 0.5 km/s, the impact speed has an upper limit of 73.4 km/s, giving an upper limit for the specific energy of a comet hitting the earth of about 2690 mj/kg.
specific energy