How can you increase efficiency of a block and tackle pulley system ? 

A crowbar is $140 \mathrm{cm}$ long and is pivoted about a point $10 \mathrm{cm}$ from its tip. What is the smallest force which should be applied at the other and to displace load of $200 \mathrm{kgf}$ ? Also find the V.R. 

In a movable pulley, the load is $100 \mathrm{N}$. Find the mechanical advantage, effort applied and V.R. if the efficiency is $100$ percentage. State two factors which reduce the efficiency.

A crowbar of length $120 \mathrm{cm}$ has its fulcrum situated at a distance $30 \mathrm{cm}$ from the load. Calculate the M.A. of the crowbar.