Shaking Doesn't Work on the iPad
The iPad has a built-in acceleromonitor that can detect short shake gestures. IOS 7 was designed to recognize the shake gesture as an "Undo" function while you are in apps such as Mail, Notes, the iWork suite and some third-party applications. However, shaking your iPad can feel awkward, and it might take a few tries to master this gesture. If the shake gesture does not work with practice, then a hardware or software issue could be preventing it from operating properly.
1 Test The Shake Gesture
Open the Notes app and type out a sentence. Grasp your iPad firmly by the sides and shake it quickly from side to side. A dialog that reads "Undo typing" should pop up. If you tap "Undo," the sentence you just wrote disappears. If you tap "Cancel" then the sentence remains on the screen.
A software or hardware issue could prevent the shake gesture from working on your iPad. Do a hard reset on your device by holding the home and sleep/wake button until the Apple logo shows. If the issue persists, back up your iPad to iTunes or iCloud and then restore your device. If these steps do not resolve the issue, make a Genius Bar appointment at your nearest Apple store (link in Resources), so technicians can troubleshoot your hardware.