I already had gazebo installed in my Ubuntu system but it wasn't working properly so tried to uninstall it using "sudo apt-get remove ros-fuerte-simulator-gazebo" command, but it says no gazebo7 package found. Then I tried to install gazebo again following the installation process told on the Gazebo .org so it gives the following error saying that some dependencies are not installed so the package installed is broken. Following is the output on the terminal screen after installation finishes:

Reading package lists... Done Building dependency tree Reading state information... Done Some packages could not be installed. This may mean that you have requested an impossible situation or if you are using the unstable distribution that some required packages have not yet been created or been moved out of Incoming. The following information may help to resolve the situation:

The following packages have unmet dependencies: gazebo7 : Depends: libgazebo7 (= 7.1.0-1~trusty) but it is not going to be installed Depends: gazebo7-common (= 7.1.0-1~trusty) but it is not going to be installed Recommends: gazebo7-plugin-base E: Unable to correct problems, you have held broken packages.