You have calculated the work done in problem (a). Subtract the work done against resistance and you have the change in kinetic energy. The original kinetic energy is given by [tex](1/2)mv^2= (1/2)(1000)(4^2)= 8000 J. Add that to the increase in kinetic energy to get final kinetic energy. Then use
b) The total mass of the train and its load is 1000kg, and the speed of the train at A is 4 m/s. Given that the work done against resistances between A and B is 13500J, calculate the speed of the train at the point B.