Question

How does the friction at fulcrum affect the mechanical advantage of a lever?

Answer 1

Mechanical advantage of the lever is equal to the ratio of effort arm to the load arm.

𝑀𝑒𝑐ℎ𝑎𝑛𝑖𝑐𝑎𝑙 𝑎𝑑𝑣𝑎𝑛𝑡𝑎𝑔𝑒 𝑜𝑓 𝑙𝑒𝑣𝑒𝑟
$=\frac{Load}{Effort}$ $=\frac{Effortarm}{Loadarm}$

Effort needed to balance the load increases due to friction at fulcrum, and hence mechanical advantage decreases.