5. Two boxes of mass 20 kg and 25 kg are connected by a rope and are to be pulled up a smooth slope inclined at 15 to the horizontal with the 20 kg box following the other. The 25 kg box is attached to a cable which is parallel to the plane and passes over a smooth pulley. The other end of a cable is attached to a sack of mass M kg which hangs freely. The sack moves downwards with an acceleration of 0.14 m 5-2_ (a) Draw a diagram to show all the forces acting on the boxes and the sack. [3] (b) C alculate the tension in the rope between the two boxes. [3] (e) Calculate the value ofM. [5] (d) In practice the acceleration of the system with these masses is less than 0.14 m s'z. Explain how the modelling assumptions need to be changed to explain this. [1]