Problem 8.79 A 4.0-kg block and a 2.0-kg block are connected to
opposite ends of a relaxed spring of spring constant 300 N/m. The
blocks are pushed toward each other for 0.5 s. The 4.0-kg block is
pushed with a force of 45 N , and the 2.0-kg block is pushed with a
force of 20 N. Ignore the inertia of the spring. Part A What is the
acceleration of the center of mass of the two-block system while
this pushing is going on? Assume that the positive direction is
from 4.0-kg block to 2.0-kg block. Part B When the blocks are
released, what is the velocity of the 0.20-kg block if the 4.0-kg
block is moving toward it at 1.6 m/s in the Earth reference frame?
Assume that the positive direction is from 4.0-kg block to 2.0-kg
block.?