When you press the power button on the iPad it really just turns off the screen. That‘s why it comes on so fast. What you may want to do to conserve battery life or recover from a freeze is do a reboot.
To do this just hold down both the power button and Home button until the red slider appears on the screen. Slide it and the iPad will shut down. Give it a minute and then you can restart it by pressing the power button again.
It seems to take a few seconds before it responds so be patient. And, to force quit an application, just hold the home button by itself in a similar fashion.
"iPad Tips and Tricks: Shut Down Your iPad For Real "
Reference : top-ipad-video-converter.com