Two or more lines lying in the same plane that tend to meet each other at infinity are known as parallel lines. In other words, two or more lines are said to be parallel lines if they do not intersect each other or do not meet each other at any point.
Properties of Parallel Lines
1. Two lines parallel to each other represent a pair of linear equations in two variables that do not possess a consistent solution.
2. The slopes of two parallel lines are equal.
3. Parallel lines are equidistant from each other.
4. When a transversal line intersects or cuts two parallel lines:
- The resultant corresponding angles are equal.
- The vertically opposite angles so formed are equal.
- The alternate interior angles are equal.
- The alternate exterior angles are equal.
- The sum of the pair of interior angles on the same side of the transversal is supplementary or is equal to 180°.
Examples of Parallel Lines
1. Railway Tracks
If you are looking for a real-life application of parallel lines, you must closely observe the railway tracks. The iron bars that make up the tracks are laid parallel to each other. In a similar manner, the sleepers are also placed parallel to each other.
2. Edges of a Ruler
A ruler is used to draw straight lines and other figures. If a line is traced along one side of the ruler and another line is drawn using the opposite side, the resultant lines will be parallel to each other. Hence, both the opposite sides of the ruler are parallel to each other.
3. Zebra Crossing
A pedestrian crossing or a zebra crossing is a portion of the road that is painted with white stripes. These white stripes are parallel to each other.
4. Cricket Stumps
One of the prominent examples of parallel lines is the cricket stumps. All the three stumps of a wicket, namely the off stump, middle stump, and leg stump, are placed at equal distances and are parallel to each other.
5. Electrical Wires
The electrical power generated by the powerhouse reaches our homes with the help of the wires attached to the electricity poles. These wires can be easily seen along the roadside. The wires are separated from each other at a distance and are parallel to each other. Hence, the electrical wires placed between the powerhouse and the homes constitute a perfect example of parallel lines in real life.
6. Racing Tracks
Racing tracks that are properly marked with broad white stripes of paint or powder constitute one of the best examples of parallel lines in real life. These white stripes are clearly parallel to each other.
7. Markings on Road
Road markings are necessary to enhance safety and security while driving. These markings include road shoulder line, centre line marking, kerb marking, traffic lane marking, etc. One can easily observe the existence of parallel lines in real life by looking at such markings on the road.
8. Ruled Paper
The lines printed on a ruled paper are equidistant from each other. These lines tend to meet each other at infinity. Hence, the lines of a ruled paper are a prominent example of parallel lines in everyday life.
9. Fork Tines
The tines of a fork are parallel to each other. Hence, if you visualize each tine of the fork as a straight line, a fork constitutes a perfect example of parallel lines.
10. Steps of a Ladder
The steps of a ladder are equidistant from each other at every instant. Also, the slope of all the steps is the same. Hence, they are parallel to each other.
11. Railing Bars
Most of the railings or fences consist of straight-line equidistant metallic or wooden bars that are placed parallel to each other.
12. Keys of a Piano
If you look at the orderly arranged keys of a piano, all of them are parallel to each other. Hence, the keys of a piano are a classic example of parallel lines.
13. Stack of Books
If you form a pile or a stack of books by placing one book on top of another, you can easily observe the existence of parallel lines in real life. The top and the base of the books act as parallel lines to each other.
The opposite sides of a rectangle or a square geometric figure are parallel to each other. Ergo, the sides of a rectangular or square-shaped table demonstrate the existence of parallel lines in real life.
15. Pins of a Plug
The pins of a two-pin or a three-pin plug are parallel to each other. Hence, they can be considered as explicit example of parallel lines.
Skis are long and tapered boards made up of flexible materials such as polyethylene, fibreglass, carbon fibres, etc. When a person fastens the ski boards under his/her feet and slides down the snowy surface, he tends to keep his feet aligned in a parallel position. Hence, parallel lines in real life can be observed by looking at the pair of skis.
17. Shelves of a Rack
A shoe rack, pallet rack, book rack, etc., consist of multiple shelves to store objects. The shelves are arranged parallel to each other. Hence, the shelves of a rack are yet another example of parallel lines in everyday life.