Question

A fixed pulley is driven by a 100 kg mass falling at rate of 8 m in 4 sec . It lifts a load of 75.0 kgf then calculate the efficiency of the pulley...

Answer 1

The efficiency of pulley is 0.75

Given:

Mass, m = 100 kg

Distance, d = 8 m

Time, t = 4 sec

Load, F = 75 kgf

Solution:

The effort is 10 N for 1 kg.

So, the effort will be for 100 kg = 1000 N

Load will also be 750 kg.  

The power (P) will be,

$P=\frac{E f f o r t \times D i s p l a c e m e n t}{T i m e}$

$P=\frac{1000 \times 8}{4}$

$P=2000 \ \text{watt}$

The efficiency will be

$\text{Efficiency} =\frac{\text {Load} \times \text { Distance }}{\text { Effort } \times \text { Distance }}$

$E=\frac{75 \times 8}{1000 \times 8}$

$\therefore E=0.75$