Question 13 Marks
A pulley system has four pulleys in all and is 60% efficient, Calculate
(a) the mechanical advantage
(b) the effort required to lift a load of 1200 N,
(c) the resistance due to the movable parts and friction of the pulley system.
(a) the mechanical advantage
(b) the effort required to lift a load of 1200 N,
(c) the resistance due to the movable parts and friction of the pulley system.
Answer
View full question & answer→(a) Velocity ratio = No. of pulleys = 4 .
Knowing, $\eta=\frac{ MA }{ VR }$
$MA=\eta \times VR-\frac{60}{100} \times 4=2.4$
(b) Also, $\frac{l}{E}= MA$ or $E=\frac{l}{ MA }=\frac{1200 N}{2.4}=500 N$
(c) Knowing, $MA = VR -\frac{x}{E}$
$\therefore x=E( VR - MA )=500(4-2.4)=800 N$.
Knowing, $\eta=\frac{ MA }{ VR }$
$MA=\eta \times VR-\frac{60}{100} \times 4=2.4$
(b) Also, $\frac{l}{E}= MA$ or $E=\frac{l}{ MA }=\frac{1200 N}{2.4}=500 N$
(c) Knowing, $MA = VR -\frac{x}{E}$
$\therefore x=E( VR - MA )=500(4-2.4)=800 N$.
