The control is what you keep the same for each one. For example if you are doing an experiment with plants say you water one with lemon juice, one with milk and one with warm water. The control would be they all have the same amount of sun light and soil. So the growing is equal to keep the experiment fair.
The best example of an object and motion that would make it hard for people to accept Newtons first law is, "A rolling ball eventully slows down and comes to a stop".
