Re: [Phys-l] heat/energy

[Leigh Palmer <palmer@sfu.ca>]

Anthony Lapinski wrote:

> I'm looking for some simple activities for a heat investigation/lab.
> Specifically, when two objects collide, I want to show how kinetic energy
> (loss) changes to work, sound, and heat. I thought about just hammering a
> nail. They can clearly see the nail going into the wood and hear the
> noise. I tried this (driving the nail about 1.5 cm), but could not really
> sense a temperature change in the nail and hammer head. I then tried
> pounding a lead brick with a sledgehammer, but both felt cool to the
> touch. Maybe this has to be done for a longer time?
>
> Does anyone have a demo/activity that "easily" shows a temperature rise
> when two objects impact?

Hugh offered the deck screw example (with which I am very familiar). Another example of simple conversion of work into easily sensible temperature rise (please don't say "heat") can be got by extracting a 16 penny box nail* from a wood two-by-four with a claw hammer in a single pull. Pound the nail in through the wide dimension, across the grain, leaving half inch length of the head protruding. Use a piece of wood as a fulcrum to increase the length of the pull stroke. If the task is sufficiently difficult, which depends upon the wood, this can also make the nail almost too hot to handle. The only advantage this has over Hugh's example is in the employment of human muscle power instead of a power tool.

(I'm acutely sensitive to the value of the battery powered portable drill/screwdriver since I spent some time last evening assembling an IKEA TV stand with casters. That tool is the single most valuable benefit of the man-in-space effort, the least valuable being the ISS, of course.)

Leigh

* I'm sure other nails would work. I have done no research on this; it's from experience that I offer this. Common nails have higher heat capacity, but they might also be harder to pull, so I don't know which would get hotter - common or box.