How do scissors work- two pivoted metal blades connected in such a way that the sharpened edges slide against each other and cut the material.

The force applied on the blade can be calculated by length of the handle and force applied on the grip of handle.  A pair of scissors is an example of two first class levers connected together at the joint known as fulcrum.

It is most likely that scissors were invented in 1500 BC in ancient Egypt. The earliest known scissors appeared in the Middle East 3,000 or 4,000 years ago. These were of the 'spring scissor' type comprising two bronze blades connected at the handles by a thin, curved strip of bronze. This strip served to bring the blades together when squeezed and to pull them apart when released.

Cross-bladed scissors were invented by the Greeks around AD 100 (plate 41A), also found in Egyptian Civilization (plate 41B). Pivoted scissors of bronze or iron, in which the blades were connected at a point between the tips and the handles, were used in ancient Rome, China, Japan, and Korea. Spring scissors continued to be used in Europe until the sixteenth century and the idea is still used in almost all modern scissors.

Mechanism of cutting :

Plate41A Ancient Greek Scissors (2nd C AD)	41B Ancient Egyptian Scissors

(Source:http://www.google.co.in/search?hl=en&q=scissors+mechanism&bav=on.2,or.r_gc.r_pw.r_qf.&
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ICw#um=1&hl=en&tbm=isch&sa=1&q=scissors+mechanism+in+ancient+Egypt&oq=scissors+
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