Question

A movable pulley is used as:

• A. force multiplier
• B. speed multiplier
• C. device to change the direction of effort
• D. all the above

Answer 1

The correct option is A force multiplier

The movable pulley reduces the effort required to pull a mass by factor of 2 $\times$ number of movable pulleys. Consider a simple example of single fixed and movable pulley.
In case I of fixed pulley the effort will be same as of load being lifted as tension in rope will be same across pulley, hence mechanical advantage will be 1.
$F_{effort}=F_{load}$
In case II of movable pulley the effort will be half of that load being lifted as the forces on mass less pulley should balance, mechanical advantage will be 2.
$2F_{effort}=F_{load}\Rightarrow F_{effort}=F_{load}/2$
Movable pulley is used as force multiplier, correct answer is option A.