Question

Figure shows a system of four pulleys. The upper two pulleys are fixed and the lower two are movable. (a) How are load and effort of the pulley system related? (b) What assumption do you make in arriving at your answer in part (a)?

Answer 1

(a) The block and tackle system consists of 4
pulleys, i.e. $n=4$
In a n-pulley block and tackle system, if the
effort is applied in the downward direction
then the tension in the n segments of the
string supports the load.
$L=nT\text{and}E=T$
So $E=\frac{L}{n}$

$\therefore \text{Load}=4\times Effort$

(b)The assumption to be made are:

1. There is no friction in the pulley bearings,
2. Weight of lower movable pulleys is
   negligible and
3. The effort is applied downwards.