Science is Magic

91

A THOUSAND NAILS ARE BETTER THAN ONE

If you were to push a balloon onto a nail (do not try this

at home!), you wouldn’t need to push very hard before

it popped. This is because all of your pushing force is

concentrated on one nail. Yet pressed onto many nails,

the balloon won’t burst—the pushing force is shared

across the nails and is not enough to pop the balloon.

The same is true with nails and the skin on a human body.

PRESSURE POINTS

When force is concentrated on a small area, we

say the pressure is high. When it’s spread out,

we say it’s low. The trick always uses blunt nails

with a larger surface area than sharp nails, so

pressure is low and the skin is not pierced.

Force is spread over

many points.

A high heel has

a small area, so the

pressure is high.

An elephant may be

heavy, but its wide foot

spreads the weight, so

the pressure is low.

Force is

concentrated

on a tiny point.

SHARP - HIGH PRESSUREBLUNT - LOW PRESSURE

HIGH-HEEL SHOE

ELEPHANT FOOT

IT’S A

LL ABOUT

PRE

SSURE!

US_090-091_Bed_of_nails.indd 91 09/10/2018 10:18