Method 1:
Remove-SPWebApplication -Identity http://ukreddy:6789
This cmdlet will ask for user's confirmation.
Remove-SPWebApplication -Identity http://ukreddy:6789 -Confirm:$false
This cmdlet won't ask for user's confirmation.
This cmdlet permanently removes the Web application at http://ukreddy:6789. This command does not remove the content databases or the IIS Web site.
Method 2:
Remove-SPWebApplication -Identity http://ukreddy:6789 -DeleteIISSite -RemoveContentDatabase
This cmdlet will ask for user's confirmation.
Remove-SPWebApplication -Identity http://ukreddy:6789 -Confirm:$false -DeleteIISSite -RemoveContentDatabase
This cmdlet won't ask for user's confirmation.
This cmdlet permanently removes the Web application at http://ukreddy:6789. This command also remove the content databases or the IIS Web site.
