For an isotope with a half-life of one day, at the end of three days the amount that remains is
A) none.
B) one-half.
C) one-quarter.
D) one-eighth.
E) none of the above
Question 2
Most asteroids are oblong in shape. Approximate an asteroid as being made up of two identical spheres of mass M and radius R that are just touching each other, in a figure eight.
In terms of G, M, and R, what is the escape velocity for a spaceship taking off from the top of the figure eight? A) (2GM/R)1/2
B) (4GM/3R)1/2
C) (8GM/3R)1/2
D) (3GM/R)1/2
E) (7GM/5R)1/2
