In article , "Ray K." wrote:
Doug Miller wrote:

Big snip


Then I suggest you do the test: arrange the weight, scale, and anchor as
shown
in your diagram above and reproduced he


SCALE
I
O
I \
I \
I \
I \
I \
I \
I Anchor
16 LB weight


and report what the scale at the top reads.

Note that we're still waiting for Harry to respond to this...

Actually, you want the anchor as close as possible to the weight, not
off at an angle. When it's some distance from the weight, depending on
how the scale is attached to the ceiling (free to pivot or rigidly
fixed), the scale will also measure some portion of the horizontal
component of the rope's tension and increase its reading, something
everyone has missed so far. (I know it won't make a 2:1 difference.)

Actually, that's been addressed by at least one of, and I think both, Michael
Daly and John Cochran earlier in this thread.

BTW, some of you referred to the How Stuff Works link,
http://www.howstuffworks.com/pulley.htm, for supposedly an authorative
explanation of pulleys (even though it doesn't address the issue here).
I see their third figure, the one with one pulley at the weight and the
other at the ceiling, as wrong. At the weight, the rope changes angle
about 60 degrees; that is, each is about 30 degrees from the vertical.
The vertical component of "each" rope's tension must be 50 pounds.
Therefore, the tension in the rope must be 50/cosine 30 = 50/.866 = 57.5
pounds.

Lesson: Don't trust even fancy websites to get simple basics right.