There is a theory that indicates that dinosaurs became extinct when about 65 mil

Question

There is a theory that indicates that dinosaurs became extinct when about 65 million years ago, a large asteroid hit the Earth surface. Since the energy of impact was high, dust was created in the atmosphere and this dust, caused by this collision, blocked the sunlight reaching the Earths surface and many forms of life became extinct due to the cold. Fearing this threat, how large an asteroid should you be looking for if the dangerous asteroid size is approximately the same as the one that killed the dinosaurs? Available data suggests that about 20 per cent of that asteroids mass ended up as a dust spread evenly over Earth after eventually settling out of the upper atmosphere. About 0.020g/cm2 of dust, which is chemically different than the Earths rock, covered the Earths surface. Typical asteroids have a density of about 2g/cm3 . Now that we know the size of the asteroid, how much energy was released during impact, assuming all of it was kinetic?

Explanation / Answer

Find out how many square cm there are on the surface of the Earth(5.1 x 1018). It'll be roughly the same area as it was 65 million years ago.

Since, 5.1e+18 is the surface area of Earth in square cm.
multiply that figure by 0.020
That's the number of grams on each sq cm. = 1.02E17
divide that figure by 0.20, since only 20% of the asteroid was pulverised and scattered across the surface.
So now you'd have the mass of the extra-terrestrial rock. = 5.1e17
Divide that figure by the average density of an asteroid, and you get the total volume of the asteroid.
Assuming the asteroid was spherical:
Volume of a sphere = 4/3 pi r3
so r, the radius will be the cube root of the 3 x volume / (4x pi)
But it'd be better to quote the diameter; it's easier to visualise.

Hope this helps :)

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