Answer to Question #328977 in Physics for Rae

Question

10. A pulley system operated with an electric motor consumes 5.0 kJ of energy as it does 3.2 kJ of work in raising an object. The efficiency of this technology is:

(a) 64% (b) 84%

(c) 119% (d) 156%

Answer 1

By definition, the efficiency is given as follows:

$\eta = \dfrac{W}{E}\times 100\%$

where $W = 3.2 kJ$ is the produced work, and $E = 5.0 kJ$ is the consumed energy. Thus, obtain:

$\eta = \dfrac{3.2 kJ}{5.0 kJ}\times 100\% =64\%$

Answer. (a) 64%.