Question

A pulley system has a single fixed pulley and a single movable pulley. Its mechanical advantage is _ _ _ _.
A. 1
B. 2
C. 3
D. 4

Answer 1

Hint: The mechanical advantage of the pulley is the ratio of the load to the effort. The movable pulley in the combination doubles the load.

Formula Used: The mechanical advantage of the pulley is,
\[{\text{MA}} = \dfrac{{{\text{Load}}}}{{{\text{Effort}}}}\]

Complete step by step answer:We have the mechanical advantage of the pulley is defined as ratio of load and effort.
\[{\text{MA}} = \dfrac{{{\text{Load}}}}{{{\text{Effort}}}}\] …… (1)

We know that, in a system of single fixed pulley and single movable pulley, the movable pulley doubles the effort,
\[L = 2T\]

Here, T is the tension in the rope.


The effort is in downward direction and it is,
\[E = T\]

We substitute T for Effort and 2T for Load in equation (1). Therefore, the mechanical advantage is,
\[{\text{MA}} = \dfrac{{2T}}{T}\]
\[ \Rightarrow MA = 2\]

So, the correct answer is option (B).

Additional information: In a single movable pulley, the effort is in the downward direction. There is no supporting rope and has no mechanical advantage. In a single movable pulley, the effort is in the upward direction. It has two supporting ropes and has mechanical advantage of 2. In a single fixed and single movable pulley system, there are two supporting ropes. The effort is in the upward direction and load is in the downward direction. The disadvantage of this system is the effort must move 2 times the distance moved by the load.

Note: In combination of single fixed pulley and single movable pulley, the movable pulley doubles the load. The effort does not change for both movable pulley and fixed pulley.