YTSS Prelim P2

NAME: ( ) CLASS: YISHUN TOWN SECONDARY SCHOOL PRELIMINARY EXAMINATION 2024 SEC 4 EXPRESS PHYSICS (6091/2) DATE : 21 August DAY : Wednesday DURATION: 1 hr 45 min MARKS: 80 marks READ THESE INSTRUCTIONS FIRST Write your name, class and register number in the spaces provided at the top of this page. Section A Answer all the questions. Write your answers in the spaces provided. Section B Answer one question. Write your answers in the spaces provided. INFORMATION FOR CANDIDATES The number of marks is given in brackets [ ] at the end of each question or part question. Candidates are reminded that all quantitative answers should include appropriate units. You may use an approved calculator. Section A /70 Section B /10 TOTAL /80 This question paper consists of 25 printed pages.

2 Section A Answer all questions. 1 Belle attends a body toning course. At the end of the course, the trainer measures the circumference of Belle’s arm and it decreases from 35 cm to 28 cm. (a) State the name of the measuring instrument used by the trainer. [1] (b) By modelling the arm as a simple cylinder that is 18 cm long, calculate the amount of volume lost through the training. volume lost = [1] (c) The density of fat is approximately 0.90 kg/m3. Assuming the mass lost are all from fat, calculate the mass lost through the training in kg. mass lost = kg [2]

3 2 Fig 2.1 shows the cross-sectional view of a simple DC motor. When current passes through the wires, they begin to spin along the dotted line about the axle of the motor. Fig 2.1 The diameter of the dotted circle is 12 cm. (a) On Fig 2.1, draw and label the force acting on each wire and label them as F. [1] (b) When the wire coil is at 30o from the horizontal, the moment generated by the motor is 7.2 Nm. Calculate the amount of force F acting on each wire. F = [2] (c) Explain why F is induced on the wire when a current flows through the wire. . . [2] (d) When the wire coil is at the vertical position, there is no moment about the axle. Explain why the wire coil would spin pass this position without any moment. . [1]

4 3 In some electrical scooters, dynamos are installed to recharge its battery pack. Fig 3.1 shows how the dynamo is turned by the front wheel of the scooter as it turns the drive wheel of the dynamo. Fig 3.1 (a) Describe the stages of energy transfer and conversion from the spinning front wheel of the scooter to the energy store in the battery. . . [2] (b) Explain how an EMF is induced across the dynamo when the wheel of the scooter turns the driving wheel of the dynamo. . . .