The string "satya prakash physics book pdf" + "saudi arabia driving computer test pdf" creates a non-sensical compound query. An interesting feature of modern search algorithms is query segmentation —the ability to detect that these are two distinct intents (Academic Textbook vs. Government Driving Exam) separated by an invisible boundary, rather than one long document title.
Here is the breakdown of the "interesting feature" you are noticing: The string "satya prakash physics book pdf" +
This appears to be a combining two completely unrelated topics. The interesting feature is how search engines (or a user's clipboard) might accidentally merge terms. The string "satya prakash physics book pdf" +