Question

If a machine is lubricated with oil ___________

(a) The mechanical advantage of the machine increases

(b) The mechanical efficiency of the machine increases

(c) Both its mechanical advantage and efficiency increases

(d) Its efficiency increases, but its mechanical advantage decreases

This question was posed to me in unit test.

My doubt stems from Coefficient of Restitution topic in section Gravitation of Engineering Physics I

Answer 1

Correct answer is (b) The mechanical efficiency of the machine increases

Easiest explanation: When a machine is lubricated with oil, energy wastage against friction decreases. This increases the mechanical efficiency of the machine.