Question

The mechanical advantage of an actual pulley is less than 1. Give a reason. What is the justification for using the pulley then?

Answer 1

Hint: To answer this question we will first learn a little about mechanical advantage. We will learn what it means and also its formula. Later we will answer why the mechanical advantage of a pulley is actually less than 1. To raise up something more force is required than raising down something.

Formula Used:
\[MA = \dfrac{{{F_0}}}{{{F_i}}}\]
Where, MA is a mechanical advantage,
\[{F_0}\]= force produced
\[{F_i}\]= force applied
\[\dfrac{{{F_0}}}{{{F_i}}}\] is the ratio of force produced to force applied.

Complete step by step solution:
Let us see what mechanical advantage is defined as: It is the ratio of force produced by a machine to force applied to it, used to evaluate machine performance.
The ideal mechanical advantage equals the length of the effort arm divided by the length of the resistance arm of a lever. In general, the MA = the resistance force, $F_0$, divided by the effort force, $F_e$
\[MA = \dfrac{{{F_0}}}{{{F_i}}}\]
When the pulley's mechanical advantage is equal to or less than one, we use it because it allows us to apply the effort downwards, in a handy direction. It is difficult to raise a load directly upwards. However, with the help of a pulley, the effort can be applied downward to move the load upwards. One can cling on to it in order to exert effort by using his own weight.
Hence the larger the advantage is the easier it will be to lift the weight, but mechanical advantage of an actual pulley is less than 1. And it is difficult to raise any load upwards.

Note:
Do not think that there are no disadvantages of mechanical advantage. When the load arm of a lever is longer than the effort arm, it is considered to be mechanically disadvantageous. The load force to effort force ratio is poor. Third-class levers are always mechanically inferior.