Bag of Lead Shot
Publication information:
Abstract
Dropping bag containing lead turns gravitational potential energy to heat.
What it shows:
A demonstration of the conversion of gravitational potential energy to heat energy. A bag of lead shot, repeatedly dropped to the ground, will heat up.
How it works:
Lead has a sufficiently low specific heat capacity (128 J/kg/K) that a 5kg bag dropped five times from a height of 1.0m onto a rigid floor should increase in temperature by about 2K. The shot is contained in a bank deposit bag with reinforced stitching; its temperature is read before and after the drops with an Omega® temperature probe (See The Supercooling of Water).
Setting it up:
Make sure the probe is placed at the center of the shot and given time to reach equilibrium. Take the final temperature immediately after the final drop. Keep a meter rule handy for height measurements. Before handing this demo to the lecturer, check the seams of the bag.
Comments:
You do get a temperature rise, but there are a lot of losses. We have yet to find a bag capable of taking the punishment of this demo, hence the underlining in Setting it Up.
Full text
Dropping bag containing lead turns gravitational potential energy to heat.
What it shows:
A demonstration of the conversion of gravitational potential energy to heat energy. A bag of lead shot, repeatedly dropped to the ground, will heat up.
How it works:
Lead has a sufficiently low specific heat capacity (128 J/kg/K) that a 5kg bag dropped five times from a height of 1.0m onto a rigid floor should increase in temperature by about 2K. The shot is contained in a bank deposit bag with reinforced stitching; its temperature is read before and after the drops with an Omega® temperature probe (See The Supercooling of Water).
Setting it up:
Make sure the probe is placed at the center of the shot and given time to reach equilibrium. Take the final temperature immediately after the final drop. Keep a meter rule handy for height measurements. Before handing this demo to the lecturer, check the seams of the bag.
Comments:
You do get a temperature rise, but there are a lot of losses. We have yet to find a bag capable of taking the punishment of this demo, hence the underlining in Setting it Up.