Some of my apps on my ipad open but become very small and i cant use them

These apps are probably meant for the iPhone/iPod touch. Some apps are universal, and other have dedicated iPad versions.

http://support.apple.com/kb/HT4082

Here is a support article addressing this.

Have you reset the iPad?

Holding the sleep/wake and home buttons simultaneously will do so.

If they problems continue you may want to consider restoring your device

http://support.apple.com/kb/HT1414