I have an especially inquisitive group this semester and they extended an
experiment in a new way which I am having trouble analyzing. I am sure it
has something to do with how I am defining the system, so that deltaL is
NOT equal to 0, but I just don't see it...
They had 2 rectangular blocks that would glide on an air table. Both
blocks have the same mass, length and width (to within our measurement
capability). They took Block 1 and Block 2 and oriented their long axes
with the y axis direction, a distance apart on the air table. They then
gave a light push to Block 1 in the +x direction toward Block 2 which was
still at rest (not easy on an air table, but they did quite well). The 2
blocks hit and stuck together at 1/4 of their length from the end; the
bottom of Block 1 1/4 from the end hit the top of Block 2 1/4 from its
end. They stuck because the students used velcro.
Now, the 2 blocks move off together in the +x direction, but they also
begin to spin/rotate cw.
I can explain the inelastic collision (I'm fairly sure). However, since I
view the 2 blocks as the system, I see no outside force and thus I can't
explain the non-conservation of angular momentum. I'm assuming I'm
defining the system wrong, so that there is a torque, but I don't see it.
Any help/nudge in the correct direction would be appreciated.