Yes I agree object can be in motion and in not motion at the same time for example there are two men travelling on the bus one person is A another person is B. the person be B rest so by seeing person be the person A also sits but the person see who saw the person be B move along with person C so the the person be B is in rest for person Abut is motion for a person C.
isotopes have the same atomic number because they are the same element but have a different atomic mass because they contain a different number of neutrons.
