A spaceship of titanium-devouring little green people has found a perfectly spherical asteroid. A narrow trial shaft was bored from point A on its surface to the centre O of the asteroid. This confirmed that the whole asteroid is made ofhomogeneous titanium. At that point, an accident occurred when one of the little green men fell off the surface of the asteroid into the trial shaft. He fell, without any braking, until he reached O, when he died on impact. However, work continued and the little green men started secret excavation of the titanium, in the course of which they formed a spherical cavity of diameter AO inside the asteroid, as illustrated in the figure. Then a second accident occurred-Another little green man similarly fell from point A to point O, and died. The ratio of the impact speeds of the first green person centre to second green person is Assignment no. 17

Kinetic friction comes into existence when there are moving surfaces means in other words we can say that the force which comes into existing between moving surfaces is known as kinetic friction.