Most geologists believe that the dinosaurs became extinct 65 million years ago w

Question

Most geologists believe that the dinosaurs became extinct 65 million years ago when a large comet or asteroid struck the earth, throwing up so much dust that the sun was blocked out for a period of many months. Suppose an asteroid with a diameter of 2.0 km and a mass of 1.2×1013 kg hits the earth with an impact speed of 4.5×104 m/s .

1. What is the earth's recoil speed after such a collision? (Use a reference frame in which the earth was initially at rest.)

2.What percentage is this of the earth's speed around the sun?

Explanation / Answer

Applying momentum conservation,

1.2 x 10^13 x 4.5 x 10^4 + 5.974 x 10^24 x 0 = (1.2 x 10^13 + 5.972 x 10^24) v

v = 9.04 x 10^-8 m/s

2) speed of earth around the sun = 30 km /s = 30 x 10^3 m/s

% = (9.04 x 10^-8 / 30 x 10^3) x 100 = 3.01 x 10^-10 %

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