AS & A Level Physics 9702_21 May_June 2021 Paper 2.

2 A person uses a trolley to move suitcases at an airport. The total mass of the trolley and suitcases is 72kg. (a) The person pushes the trolley and suitcases along a horizontal surface with a constant speed of 1.4ms–1 and then releases the trolley. The released trolley moves in a straight line and comes to rest. Assume that a constant total resistive force of 18N opposes the motion of the trolley and suitcases. (i) Calculate the power required to overcome the total resistive force on the trolley and suitcases when they move with a constant speed of 1.4ms–1. power = ..................................................... W [2] (ii) Calculate the time taken for the trolley to come to rest after it is released. time = ...................................................... s [3] (b) At another place in the airport, the trolley and suitcases are on a slope, as shown in Fig. 2.1. trolley and suitcases X Y slope 18N 9.5m F, 54N Fig. 2.1 (not to scale) The person releases the trolley from rest at point X. The trolley moves down the slope in a straight line towards point Y. The distance along the slope between points X and Y is 9.5m. The component F of the weight of the trolley and suitcases that acts along the slope is 54N. Assume that a constant total resistive force of 18N opposes the motion of the trolley and suitcases. 7 © UCLES /21/M/J/21 [Turn over (i) Calculate the speed of the trolley at point Y. speed = ................................................ ms–1 [3] (ii) Calculate the work done by F for the movement of the trolley from X to Y. work done = ...................................................... J [1] (iii) The trolley is released at point X at time t = 0. On Fig. 2.2, sketch a graph to show the variation with time t of the work done by F for the movement of the trolley from X to Y. Numerical values of the work done and t are not required. 0 work done t 0 Fig. 2.2 [2] (c) The angle of the slope in (b) is constant. The frictional forces acting on the wheels of the moving trolley are also constant. Explain why, in practice, it is incorrect to assume that the total resistive force opposing the motion of the trolley and suitcases is constant as the trolley moves between X and Y. ................................................................................................................................................... ............................................................................................................................................. [1] [Total: 12] 8 © UCLES /21/M/J/21 3 A pendulum consists of a solid sphere suspended by a string from a fixed point P, as shown in Fig. 3.1. h θ X Y P string momentum 0.72Ns 0.93 m sphere Fig. 3.1 (not to scale) The sphere swings from side to side. At one instant the sphere is at its lowest position X, where it has kinetic energy 0.86J and momentum 0.72Ns in a horizontal direction. A short time later the sphere is at position Y, where it is momentarily stationary at a maximum vertical height h above position X. The string has a fixed length and negligible weight. Air resistance is also negligible. (a) On Fig. 3.1, draw a solid line to represent the displacement of the centre of the sphere at position Y from position X. [1] (b) Show that the mass of the sphere is 0.30kg.