This article explains how to restart an iPad and, if it is not responding, how to force it to restart. It also includes other options for resetting an iPad.
How to Force Restart an iPad (All Models)
A basic restart, where you turn your iPad off and back on, is the easiest thing to do and the first thing you should try if you’re experiencing hardware problems. The process doesn’t delete your data or settings. Follow these steps:
The steps you take depend on whether your iPad has a Home button:
Hold the button until a slider appears at the top of the iPad screen.