### Physics Word Problems

**The Subject Is Optics**

From Gary White, Director, Society of Physics Students, in my e-mail today:

**The Bricklayer's Woes**

Of course, this reminds me of this classic Physics test problem which I ran into years ago, the one about this unfortunate bricklayer who loads bricks in a barrel on a pulley, then goes on a ride due to unbalanced forces and such. The original problem has many steps, but asks simply how long does this adventure take "assuming no additional collisions between bricklayer and the barrel of bricks which would add more insult to the injury".

The story showed up in Season 1 Episode 3 of

*The Mythbusters*, one of the finest science & engineering shows on television

*evah*!

In looking on Google for the original reference, I did find the Bricklayer's Report, and unbelievably, The Bricklayer's Song. And a little more history of this as an urban legend.

But I don't have all my old tests on this laptop, so I can't dredge up my copy of the test. However,

*The Bricklayer's Song*referenced above does include an assignment:

(1) Bricklayer’s Song Assignment

(1) Refer to the words of the Bricklayer's Song. Assuming there is no friction in the bricklayer's pulley and rope system, estimate the total amount of time that elapses during the injurious events described by the poor bricklayer in the song. (2) If friction were considered, what effect would this have on your estimated time? Would the actual time be smaller, larger or the same as the one you estimated?

To the instructor: Students in a typical physics class may need one or more of the following hints to get started. Hints: (1) To make this estimate you need to figure out approximate values for the height of the building, the mass of the bricklayer, and the mass of the bricks and the barrel. Then, you will need to use the Atwood's equation; (2) Although your answer should be similar to that obtained by others, there is no single "right" answer as you are being asked to make reasonable estimates; (3) You’ll need to use the Atwood’s equation to determine the Bricklayer’s acceleration in each part of his journey. You cannot simply assume that all of the bricklayer's travels occur at a = –9.8 m/s2.

You have twenty-five minutes and may use a calculator and your formula card, but no other help. Results may be posted in the comments. (grin)

Dr. Phil