AQA A-level PHYSICS 7408/3BC Paper 3 Section B Engineering physics Version: 1.0 Final *JUN2374083BC01* IB/M/Jun23/E7 7408/3BC// QUESTION PAPER & MARKING SCHEME/ [MERGED] Marl( scheme June 2023

AQA A-level PHYSICS 7408/3BC Paper 3 Section B Engineering physics Version: 1.0 Final *JUN2374083BC01* IB/M/Jun23/E7 7408/3BC For Examiner’s Use Question Mark 1 2 3 4 5 TOTAL Thursday 15 June 2023 Morning Materials For this paper you must have: • a pencil and a ruler • a scientific calculator • a Data and Formulae Booklet • a protractor. Instructions • Use black ink or black ball-point pen. • Fill in the boxes at the top of this page. • Answer all questions. • You must answer the questions in the spaces provided. Do not write outside the box around each page or on blank pages. • If you need extra space for your answer(s), use the lined pages at the end of this book. Write the question number against your answer(s). • Do all rough work in this book. Cross through any work you do not want to be marked. • Show all your working. Information • The marks for questions are shown in brackets. • The maximum mark for this paper is 35. • You are expected to use a scientific calculator where appropriate. • A Data and Formulae Booklet is provided as a loose insert. Please write clearly in block capitals. Centre number Candidate number Surname Forename(s) Candidate signature I declare this is my own work. A-level PHYSICS Paper 3 Section B Engineering physics Time allowed: The total time for both sections of this paper is 2 hours. You are advised to spend approximately 50 minutes on this section. 2 *02* IB/M/Jun23/7408/3BC Section B Answer all questions in this section. 0 1 . 1 One equation used in translational dynamics is: force = mass × acceleration State in words the equivalent equation used in rotational dynamics. [2 marks] Figure 1 shows two identical uniform plates A and B. The axis of rotation of each plate is shown. Figure 1 0 1 . 2 State and explain which plate has the greater moment of inertia about its axis of rotation. [2 marks] Do not write outside the box 3 *03* Turn over ► IB/M/Jun23/7408/3BC Do not write outside the An electric motor drives a machine that punches out plates from a box long strip of sheet metal. The motor runs continuously and is fitted with a flywheel. Figure 2 shows how the angular velocity ω of the flywheel varies with time t. Figure 2 Table 1 describes the sequence for the machine after it has been brought up to speed ωA. Table 1 A The punching operation starts. A to B The flywheel transfers some of its energy during the punching operation. B to C The flywheel is again brought up to speed ωA by the motor. C The next punching operation starts. 0 1 . 3 A new flywheel with a greater moment of inertia is fitted in place of the original flywheel. The motor torque is constant and the same as before. Sketch on Figure 2 a graph showing how the angular velocity varies with time for the machine fitted with the new flywheel. Assume that: • the punching operation starts at the same angular speed ωA • the same quantity of energy is transferred when punching the metal sheet. [2 marks] Question 1 continues on the next page 4 *04* IB/M/Jun23/7408/3BC Do not write outside the 0 1 box . 4 Explain one difference between your graph and the original graph. [1 mark] 7 5 *05* Turn over ► IB/M/Jun23/7408/3BC Do not write outside the 0 2 box Figure 3 shows a heavy stone grinding wheel used for sharpening tools. Figure 3 The pedal is connected to the axle of the wheel by a connecting link and crank. The operator pushes the pedal downwards to accelerate the wheel from rest. The wheel begins to rotate in the direction shown. 0 2 . 1 Explain why the torque applied to the axle varies as the operator pushes downwards on the pedal. [2 marks] Question 2 continues on the next page 6 *06* IB/M/Jun23/7408/3BC Do not write outside the 0 2 box . 2 The wheel is rotating at a high angular speed. The operator is told not to use the pedal to stop the rotation of the wheel suddenly. Explain, with reference to angular impulse, why a sudden stop is likely to damage the mechanism. [2 marks] 0 2 . 3 The connecting link breaks. At this instant the angular speed of the wheel is 13.8 rad s−1 . It takes 15.0 s for the wheel to come to rest. The frictional torque acting at the axle bearings is 0.77 N m and is constant for all speeds. Calculate the moment of inertia of the whee