6. Three particles, A, B and C, are attached by light inextensible strings AB and BC. Particles A and B are held at an equal height of 2 m above a horizontal floor. B rests on a rough horizontal surface and when in motion experiences a constant resistive force of P N. The string passes over two smooth pulleys. 8 kg B A C 3.5 kg 5.2 kg 2 m The masses of the particles are 5.2 kg, 8 kg and 3.5 kg respectively. It is given that B does not reach either pulley during any part of the motion following release. The particles are released and A hits the ground 4 seconds later. (a) Find the tension in each of the strings AB and BC. [5] (b) Find the exact value of P. (c) Explain how you have used the modelling assumption that the pulleys are smooth. [1] The particle A detaches from the string as soon as it hits the floor. (d) Find the acceleration of the system when C is moving downwards. [4]