Turn over 19 Question 5 continued _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ (Total for Question 5 is 10 marks) 20 6. θ 2 kg 4 kg A P B 3 m Figure 4 Two blocks, A and B, of masses 2 kg and 4 kg respectively are attached to the ends of a light inextensible string. Initially A is held on a fixed rough plane. The plane is inclined to horizontal ground at an angle θ, where tan θ = 3 4 The string passes over a small smooth light pulley P that is fixed at the top of the plane. The part of the string from A to P is parallel to a line of greatest slope of the plane. Block A is held on the plane with the distance AP greater than 3 m. Block B hangs freely below P at a distance of 3 m above the ground, as shown in Figure 4. The coefficient of friction between A and the plane is μ Block A is released from rest with the string taut. By modelling the blocks as particles, (a) find the potential energy lost by the whole system as a result of B falling 3 m. (3) Given that the speed of B at the instant it hits the ground is 4.5 m s–1 and ignoring air resistance, (b) use the work-energy principle to find the value of μ (6) After B hits the ground, A continues to move up the plane but does not reach the pulley in the subsequent motion. Block A comes to instantaneous rest after moving a total distance of (3 + d) m from its point of release. Ignoring air resistance, (c) use the work-energy principle to find the value of d (4) _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________