A-level PHYSICS Paper 3 Section B Engineering physics

aterials 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/Jun21/7408/3BC Section B Answer all questions in this section. 0 1 A gymnast dismounts from an exercise in which he swings on a high bar. The gymnast rotates in the air before landing. Figure 1 shows the gymnast in three positions during the dismount. Figure 1 The arrows show the direction of rotation of the gymnast. In position 1 the gymnast has just let go of the bar. His body is fully extended. Position 2 shows the rotating gymnast a short time later. His knees have been brought close to his chest into a ‘tuck’. Position 3 is at the end of the dismount as the gymnast lands on the mat. His body is once again fully extended. Do not write outside the box 3 *03* Turn over ► IB/M/Jun21/7408/3BC Do not write outside the 0 1 box . 1 Explain why the moment of inertia about the axis of rotation decreases when his knees are moved towards his chest. Go on to explain the effect this has on his angular speed. [3 marks] Table 1 gives some data about the gymnast in position 1 and in position 2. Table 1 Position Moment of inertia / kg m2 Angular speed / rad s−1 1 13.5 ω 2 4.1 14.2 0 1 . 2 Calculate the angular speed ω of the gymnast in position 1. [1 mark] ω = rad s−1 Question 1 continues on the next page 4 *04* IB/M/Jun21/7408/3BC Do not write outside the 0 1 box . 3 The gymnast stays in the tuck for 1.2 s. Determine the number of complete rotations performed by the gymnast when in the tuck during the dismount. [2 marks] number of complete rotations = 0 1 . 4 The gymnast repeats the exercise. The height of the bar remains unchanged. State and explain two actions the gymnast can take to complete more rotations during the dismount. [4 marks]