010-Inertia and Pressure With Assistance of Bed-of-Nails

Physics Demo Number: 010

Approximate Run Time: 10 min

Inertia and Pressure With Assistance of Bed-of-Nails

Demo Description

A bed of nails, a heavy steel plate ,and a sledgehammer are used to show how forces on an observer can be moderated to be reasonably safe by spreading them out and introducing inertial resistance into the mix.

Scientific Principles

Inertial tempering of force.

Redistribution of force by spreading over more area.

Equipment

A Bed of nails (NB) with a dedicated lab cart (RLC)
A 55lb slab of steel (AAA)with handles (A), plus soft handle(AA). The handles and soft handles have been removed in 2009.
Sledgehammer (B)
Lab coat (LC)
Wooden block (WB) and Nail (N)
Paper

Equipment Location

The basic location of the nail bed and lab coat is on the pictured dedicated cart (which lives in SC4221B).

The hammer, nail block, and steel slab stay in Kit(010) which is the next-to-top shelf of dedicated steel cart in Aisle [E-F].

Instructions

Pictured is equipment for doing inertia and pressure demos.

(NB) and (RLC) are the bed of nails and the recommended lab cart for the bed to rest on while in use by instructor. Allowing any student to lie on the nail bed is strongly discouraged.

(AAA) is a 55lb slab of steel with handles, (A), and soft handle (AA).

(B) is an 8lb sledgehammer with short handle for hammering on lecturer’s chest [with (AAA) as at least one intermediate layer between hammer and chest].

(WB) and (N) are a wooden block and a 20- penny nail to serve as the topmost layer between hammer and chest.

(LC) is a lab coat which lives on the cart and which is handy to avoid snags on clothes from the sharp heads of the nails.

Exercise extreme caution when getting on and off nail bed. (Remember not to push on nails with hands while getting on or off.) Trying to bust concrete blocks on chest with sledgehammer, either while on the bed or off, is STRONGLY DISCOURAGED.

With proper care one may have the other half of the bed placed as the first layer on the chest to make a nail- bed sandwich (not recommended for female faculty).

The second and third pictures show the apparatus in use, with proper attention being paid to the placement of hands. The book makes a good replacement for a Turban, to protect the head and scalp.

One may place a sheet of paper between the back and the nails to get a visual record of how many nails actually supported the load and hence calculate some pressure data.

Probably best not to enlist student assistance with this entire demo.