an asteroid has a mass of about 4.0×10^16kg and an (average) radius of about 16 km.

1)Calculate the speed with which you would have to throw a rock to put it into orbit around the asteroid near the surface.

2)How long would it take for your rock to return and hit you in the back of the head?

Question

an asteroid has a mass of about 4.0×10^16kg  and an (average) radius of about 16 km.

1)Calculate the speed with which you would have to throw a rock to put it into orbit around the asteroid near the surface.

2)How long would it take for your rock to return and hit you in the back of the head?

anonymous · Answer

1) 

Orbital velocity at height "h" above the surface is given by
   $$v= \sqrt{GM/(R+h)}$$
   In your problem h=0, M and R are given

2)

  Time period of one complete oscillation is naive if we know orbital velocity and radius.$$T = 2\pi R/v$$