Is collision possible even without actual contact of colliding particles ? justify .
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ANSWER
In science, language is specific and unambiguous. That means that terms are defined in ways often different from colloquial usage.
I'll quote Wikipedia on the definition of a collision. "A collision is an event in which two or more bodies exert forces on each other for a relatively short time." Note that there is no requirement for contact.
Of the four fundamental forces, both electromagnetism and gravity are long range. Despite being long range, they both fall with the inverse square of the distance (for simply distributed objects). This means you can mostly ignore the effects of the force at large distances relative to their closest approach.
A charged particle being deflected by another charged particle as they pass by each other is an example of a collision where no contact takes place. A gravitational slingshot where a small object moves around a much heavier object to gain speed is another example.