What is the efficiency of an engine that does 80 j of work and exhausts 320 j of heat while taking in 400 j of heat ? a. 10% b. 20% c. 80% d. 25%

b. 20%

Explanation:

Efficiency of an engine is a ratio in percentage of the work done to the energy intake of the engine.

η=(Q₁-Q₂)/Q₁×100%

η is efficiency, Q₁ is the energy intake, Q₂ is energy wasted.

The information provided is:

Energy intake = 400 J

Work done = 80 J = (400-320) =Q₁-Q₂

Energy wasted =320 J

η= 80/400×100%

=20%

the motion of a pendulum is a classic example of mechanical energy conservation. a pendulum consists of a mass (known as a bob ) attached by a string to a pivot point. as the pendulum moves it sweeps out a circular arc, moving back and forth in a periodic fashion.