1. I have heard the arguement that "the Effort ( Force ) required to move a certain mass by Pulling is greater than the Effort required to move the same mass by Pushing it". What is the truth regarding this statement and what causes the difference in the applied force to move the same magnitude of mass if at all there exsists a difference. 2. Secondly I have always seen that there is an Additional Engine attatched in the middle of a very long train ( esp. goods/freight carriers with large number of wagons in comparison to passennger carriers) or for trains with steep uphill routes. a. I want to know that How exactly does this combination work and help in the easier motion of the train ie how does the Pull of the front engine and Push of the second engine act on the wagons and provide the force togehter. b. How exactly does the Pull of the front engine affect the second engine and the push of the second engine affect the motion of the front engine and the wagons ahead of itself. c. Is there any interrelation which may affect the forces exerted by each of them or do these push of one and pull of other influence the resultant force exerted by the combination. ( because it seems that the additon of the second engine causes a reduction in the effort which would otherwise be exerted if a single engine of the total HP of the combination was used).