: Consider the following statement made by a student about each of the four motions in problem The magnitude of the force exerted by the Mock on an individual string is the same as the magnitude of the force exerted by that string on the block. They are a third law force pair. So I don't understand why the block doesn't move at constant speed if that is true.
" The student has correctly identified a Newton's third law (act ion-react ion) force pair. Explain why this does not mean that the block must move at constant speed.