An analogy: a child with blocks and constraints on physical
systems. A certain child’s room is
partitioned into 100 squares. His toy box in the corner is
exactly one square in size and contains
some number of blocks. When he plays with the toys, he tends
to throw them around and evenly
scatter them about the room.
a) Assume that there are now three blocks (red, green, and
blue). Also assume that all three blocks
can fit on one square. How many accessible microstates are
there for this system, if they are all
in the toy box, lid is closed, and the lid is locked in the
closed position? (All the other constraints
imposed in the story still apply.)
b) What is the total number of accessible microstates for this
system, if the toy-box lid is opened?
c) If the boy plays for a long time with all the blocks (and
randomly leaves them in the toy box or on
one of the floor squares), what is the probability of finding
the red block in the toy box, the blue
box on square #15, and the green block on square #75? Explain
how you determined this result.
d) Again, after a long time, what is the probability of
finding the red block in the toy box independently
of where the blue and green blocks are?
e) How would probability in (d) change if we asked for it
after the boy had been playing for only 15
seconds? Explain why.
f) Explain what condition must be satisfied to say that a
system is equally likely to be in any of its
accessible microstates