How is friction an advantage and a disadvantage in a lever?
In an ideal case, on a mathematical model a lever may not have any friction but in a real life situation a lever would always have a certain amount of friction at the pivot points – e.g. a manually operated water pump handle or lever. A manually driven wheelbarrow, electrically or manually operated rail-road crossing gates etc. In engineering terms friction would always be considered as a loss or disadvantage.
