Chapter 30, Problem 35A

Focal-length variations in birds and reptiles are accomplished by eye muscles that change lens thickness and curvature. For near vision, should the lens be made thicker and more curved or thinner and less curved?

To determine

To state the phase in which hot gases are expelled out of a four-stroke engine.

Explanation of Solution

Introduction:

A device which converts thermal energy into mechanical energy utilising some chemical energy in it is called a heat engine. An example of this engine is car’s engine.

All heat engines contain an internal combustion engine which burns fuel inside a set of cylinders. Each cylinder consists piston which continue moving up and down. These upward and downward movement of pistons is called a stroke. The automobiles repeat four strokes in one cycle. These four strokes are classified into the following as per their function: intake, compression, power and exhaust strokes respectively. So in the last phase of each cycle, the hot gases formed in the engine are expelled out which is called the exhaust stroke.

Conclusion:

Out of the four phases of a four stroke engine, the waste gases are removed in the exhaust stroke.