Why expiry of F&O pull down the cash market? Whats the catch?

F&O contributes to over 90% of the market turnover. Even though theoretically the cash market should drive the F&O, but what actually happens is otherwise. This gets accentuated even more during the expiry time, as the F&O volumes go out of the roof.

Check these two answers as well:

http://tradingqna.com/8466/should-looking-underlying-futures-corresponding-instrument?show=8466#q8466

​http://tradingqna.com/389/relation-between-open-interest-volume-for-futures-trading?show=389#q389

Thanks for your reply, nithin!! I am new to F&O, what is your advice for newbie like me other than practicing?

Most important aspect of F&O is money management, don’t trade with more than 10% of your capital on a single trade.