A gnome has been told by his boss to push a large rock off the road. He goes to push it, but then stops as he recalls a lesson on Newton's third law. He says to his boss, "the push from me onto the rock is going to equal the push from the rock onto me. So, I am never going to exert a greater force and will never start the rock moving." You, as the gnome's boss, must reply to the objection and briefly explain why it is incorrect.