Question

What is a pulley? What is a single movable pulley and how much M.A does it provide? How does one use a single fixed pulley along with such a pulley to apply the force in a convenient direction?

Answer 1

Definition of the pulley.

1. A grooved wheel, along with a rope or a chain to lift pails of water or heavy objects like car engines, etc.
2. This arrangement of a grooved wheel along with a rope or a chain is also a simple machine and is known as a pulley.

Single movable pulley.

1. A single movable pulley is able to move over the rope through the groove. Its axis of rotation is not fixed.
2. One end of the rope is fixed and effort is applied to the other end of the rope. The load that is to be moved is hung on a hook of the pulley. It is used to move or lift loads.
3. A movable pulley decreases the effort required to move the load,
4. Mathematically, we can see that, according to newton's second law,

$$\begin{gathered} \sum _{}\mathrm{F}={\mathrm{ma}}_{\mathrm{y}} \\ \mathrm{T}+\mathrm{T}-\mathrm{L}=0 \\ 2\mathrm{T}-\mathrm{L}=0 \\ \mathrm{T}=\frac{\mathrm{L}}{2} \\ \mathrm{or}\mathrm{E}=\frac{\mathrm{L}}{2} \\ \mathrm{Mechanical}\mathrm{advantage}=\frac{\mathrm{load}}{\mathrm{effort}}=\frac{\mathrm{L}}{\mathrm{E}}=\frac{\mathrm{L}}{\mathrm{L}/2}=2 \end{gathered}$$

5. The mechanical advantage of a single movable pulley is 2.

Single fixed pulley.

1. A single fixed pulley is fixed on support and has a fixed axis of rotation.
2. It helps us to lift a load easily by changing the direction of the force.
3. With the help of the pulley arrangement, the effort is being applied at the other end of the string in the downward direction which is accompanied by the weight of the person who is applying the effort to raise the load effectively.
4. The single fixed pulley does not decrease the effort but changes its direction for easy lifting of load.
5. The mechanical advantage of a single fixed pulley is 1.

Thus, in the case of a single fixed pulley effort is equal in magnitude to the load whereas in a single movable pulley effort is half of the magnitude of the load.