NJC 2022 SH1 Promo Paper 2 QnA_with Examiner_s Comments_latest

1 NATIONAL JUNIOR COLLEGE SENIOR HIGH 1 PROMOTIONAL EXAMINATION Higher 2 CANDIDATE NAME SUBJECT CLASS REGISTRATION NUMBER PHYSICS Paper 2 Structured Questions Candidate answers on the Question Paper. No Additional Materials are required. 9749/02 30 September 2020 2 hours READ THE INSTRUCTION FIRST Write your subject class, registration number and name on all the work you hand in. Write in dark blue or black pen on both sides of the paper. You may use a HB pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. The use of an approved scientific calculator is expected, where appropriate. Answers all questions. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question. For Examiner’s Use 1 / 9 2 / 6 3 / 6 4 / 8 5 / 10 6 / 10 7 / 15 8 / 16 Total (80m) This document consists of xx printed pages and x blank page.

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4 Answer all the questions in the spaces provided. 1 (a) (i) Distinguish between random and systematic error. ……………………………………………………………………………………………… ……………………………………………………………………………………………… ……………………………………………………………………………………………… ……………………………………………………………………………………………… [3] Suggested Solution: • Systematic errors have same magnitude while random errors have different magnitude. Or Systematic errors are predictable depending on the conditions while random errors are not. • Systematic errors are either consistently larger or smaller than the true value while random errors scatter about a mean value. (refers to sign of the error) • Systematic error can be eliminated by identifying and remo ving the error while random error can only be reduced by averaging. Examiner’s Comments: Many students failed to appreciate that 3 marks are awarded for 3 independent points. Some students tried the give examples to distinguish the two. A handful of students mixed up random and systematic errors (ii) Explain why using a graph a nd drawing line of best fit for the different points will reduce the random error. ……………………………………………………………………………………………… ……………………………………………………………………………………………… [1] Suggested Solution: In drawing the line of best fit, outliers can be eliminated. The line of best fit is drawn to accommodate as much of the data as possible by cutting in between the set of data points. In this way, the data is averaged, with most weighting given to the most similar values. This reduces the effects of random error. Examiner’s Comments: Some students unsuccessfully try to paraphrase the question to answer the question.

5 (b) A ball approaches a ramp with an inclination of 30°. It hits the surface of the ramp at a speed of 5.0 m s −1 at 45° to the normal and bounces off with a speed of 5.0 m s−1 as shown in Fig. 1.1.