A monkey hangs from a tree in a jungle and is discovered by a hunter who decides to shoot it. Pointing the rifle between the eyes of the monkey he prepares to pull the trigger. The monkey, being fairly intelligent reasons that if he waits until the moment the bullet leaves the barrel and then drops out of the tree the bullet will pass over his head.
The hunter now pulls the trigger, the monkey waits until the bullet is leaving the barrel and lets go - to his dismay the bullet hits him directly between the eyes! He was intelligent but had forgotten his Physics!
An explanation of this is shown by the experiment in the animation. An electromagnet is mounted in a clamp about 0.5 m above the bench and a blowpipe fixed horizontally in another clamp so that it is pointing just below the core of the electromagnet. A marble is put in the blowpipe and a small strip of aluminium foil fixed across the mouth of the blowpipe. The electromagnet, a d.c power source and the aluminium strip are connected in series. The power supply is switched on and the tin lid hung from the electromagnet making sure that the blowpipe is pointing at the centre of the tin.
When you blow sharply down the pipe and the marble will fly out, breaking the foil, causing the tin to fall. The marble will fall at the same rate as the tin and should collide with it before hitting the bench.