Question

A fixed pulley is driven by a 100 kg mass falling at
a rate of 8.0 m in 4.0 s. It lifts a load of 75.0 kgf.
Calculate :
(a) the power input to the pulley taking the force of
gravity on 1 kg as 10 N.
(b) the efficiency of the pulley, and
(c) the height to which the load is raised in 4.0 s.​

Answer 1

$\large\red{\bold{\underline{{ Answer\:is\:2000 w\:0.75 \: :}}}}$

The Power in Pulley will be 2000 w and the Efficiency of the Pulley will be 0.75 J

${\boxed{\bold{\underline{{Solution\:with\:Explanation}}}}}$

Given Data

• The Effort is given 10 N for 1 kg.

• Mass = 100 kg

• Time = 4 sec

• Distance = 8 m

• Load = 75 kg

Therefore,The Effort will be for 100 kg = 1000N

Solution

Load will also be 750 kg.

The Power input to the pulley taking the force of Gravity force on 1 kg as 10 N :-

Power = $\large\green{\bold{\frac{Efforts \: \times Displacement}{Time}}}$

P = $\large{\bold{\frac{1000 \: \times 8}{4}}}$

P = 2000 watt

The Efficiency of the Pulley :- $\large\red{\bold{\frac{Load \times Distance}{Effort \times Distance}}}$

E = $\large{\bold{\frac{75 \times 8}{1000 \: \times 8}}}$

E = 0.75 Joules