Question

Scissors and shears are levers of first order. However, the cutting edge of scissors used for cutting cloth is much longer than the cutting edges of shears used for cutting metals. Explain the difference.

Answer 1

Metal offers much greater resistance to cutting than cloth. In shears used for cutting metal, the cutting edge (load arm) is kept short and the handles (effort arm) are made long. This increases mechanical advantage, so a smaller effort can produce a larger cutting force. Cloth offers less resistance, so scissors can have a longer cutting edge, which makes it easier to cut a longer length at once.