Question

Shears, used for cutting metals and scissors used for cutting clothes are both examples of levers of first order. However, whereas the shears always have short blades and long handles, the scissors often have blades much longer than the handles. Explain, why this is so?

Answer 1

The mechanical advantage of an (ideal) liver equals the ratio between-the effort arm to the load arm. 

For the shears (used for cutting metals), the ‘load’ is really a formidable one. Therefore, we need a large mechanical advantage to keep the applied effort with in reasonable limits. To ensure this, the shears are made to have short blades (small load arm) and long handles (long effort arm). 

For the scissors (used for cutting clothes), the ‘load’ is an almost negligible one. Mechanical advantage, therefore, here may be more or less than one. The scissors, therefore, often have blades much longer than the handles.