Once upon a time a
monkey lived in a far off forest. A hunter, having followed the monkey for days finally saw him
hanging from a tree. The hunter raised his gun, aimed the barrel at a spot between the monkey's
eyes and fired. Now the monkey was an intelligent monkey. He realized that the last moment that
he could wait to move to avoid being hit as just after the bullet had left the barrel. This would give
him the longest possible time and the hunter cold not affect the path of the bullet by moving the
gun.
He let go and fell, just as the bullet left the gun.
Unfortunately although he was an intelligent monkey he was no good at
physics and the bullet still hit him right between the eyes. Why?
The point is that all objects fall with the same acceleration – in this case the monkey and
the bullet. As the monkey fell so did the bullet and when the bullet reached the monkey they had
both fallen the same distance and so it hit him between the eyes instead of passing over his
head!
The diagram shows the
laboratory simulation of this with the blowpipe replacing the gun and the tin lid replacing the
monkey. The marble breaks the foil link across the mouth of the blowpipe, cutting off the current to
the electromagnet and so releasing the tin lid at the same moment.
The slower the bullet
the further will the monkey have fallen before the bullet hits him – but he will still be
hit.
(We have ignored air resistance in this story. Not that it makes much difference to the
bullet!!)
