At the Same Instant That a 0

Multiple Choice

At the same instant that a 0.50-kg ball is dropped from 25 m above Earth, a second ball, with a mass of 0.25 kg, is thrown straight upward from Earth's surface with an initial speed of 15 m/s.They move along nearby lines and pass without colliding.At the end of 2.0 s the velocity of the center of mass of the two-ball system is:

A) 11 m/s, down
B) 11 m/s, up
C) 15 m/s, down
D) 15 m/s, up
E) 20 m/s, down