2022/23 CHS Physics Practical PLANNING Notes

1 Name: ( ) Class: 4 - Catholic High School 2023 Level 4 Physics Practical Planning No. Contents Page 1 Singapore-Cambridge General Certificate of Education Ordinary Level (2018) (Syllabus 6091 - Physics) 2 2 Planning Content 4 3 Example 1 – O-Level Specimen Paper 3 (Physics Syllabus 6091) 12 4 Example 2 – Physics Syllabus 5052 Nov 2008 16 5 Practice • Practice 1 • Practice 2 19 22

2 (1) Singapore -Cambridge General Certificate of Education Ordinary Level (2018) (Syllabus 6091 - Physics)

3

4 (2) Planning Content Planning questions are generally extension of existing short practical questions. Hence, students will need to be familiar with the procedure outlined in order to answer the planning question. These questions typically require the students to verify a hypothesis or relationship that may be based on an equation. For example, students may have already measured the time taken for a rod to roll down a slope as shown. The planning question may be as follows: EXAMPLE It has been suggested that the distance travelled by the rod along the slope and the time it takes is given by: t2= 2D a where D is the distance rolled down by the rod, t is the time taken for the rod to reach the bottom, and a is the acceleration of the rod along the slope. Plan an experiment to investigate the equation given. In your plan, you should: • identify the constant variables • describe how you will perform the experiment • sketch the graph that you will obtain if the suggested relationship is correct • explain how you will find a from the graph. In the next few sections, we will learn how to answer a planning question using the example above.

5 (A) Identify linear relationship of given equation When the question involves the investigation of an equation, students are expected to recall the standard linear form, y = mx + c They are also expected to rearrange relationships into linear form where appropriate. In general, the independent variable is contained within the expression for x, while the dependent variable is contained within the expression for y (see Section B for more details). EXAMPLE For the equation in the example above, we compare it against the linear form as follows: y = m x + c t2 = 2 a D + 0 Hence, we have y = t2 x = D m = 2 a c = 0 PRACTICE A1 Investigate the relationship between the object distance and image distance for a given lens, given by the lens equation 1 f = 1 u + 1 v where f is the focal length of the lens, u is the distance of the object from the lens i.e. object distance v is the distance of the image from the lens i.e. image distance Rearrange the given equation to the standard linear form and express y, m, x and c in terms of f, u and / or v. Rearranging into standard linear form 1 v = - 1 u + 1 f Hence, we have y = 1 v x = 1 u m = -1 c = 1 f

6 (B) Identifying key variables for a given question / problem There are 3 types of variables in a question or problem. 1. Independent variable: a variable with values that are selected or changed by the investigator. It is the variable drawn on the x-axis. 2. Dependent variable: a variable with values that are measured for each change in the independent variable. It is the variable drawn on the y-axis. 3. Control variable(s): a variable which could affect the independent variable and has to be kept constant to ensure a fair test. It is not necessary that every planning question will require students to list down the constant variables. In addition, it is also not necessary to describe how to keep those variables constant unless the question requires it. EXAMPLE For the rod rolling down the slope, the variables are given as follows: Independent variable: Distance rolled by the rod Dependent variable: Time taken to roll the distance Constant variable(s): Initial speed of the marble; Angle of the slope (Avoid variables (e.g. colour of marble, density of marble) which do not affect the value of the dependent variable for a specific value of the independe variable even if they are changed)

7 PRACTICE B1 Suppose I want to investigate how the length of thread in a pendulum affects its oscillation. State the independent, dependent and constant variables in this investigation. Independent variable: Length of thread Dependent variable: Period of oscillation/ Time taken for one oscillation Constant variable(s): Initial angle of release; Position of bob to measure one oscillation; Mass of pendulum bob; Number of oscillations; PRACTICE B2 Suppose I want to investigate how the number of turns of coil affects the number of paper clips attracted to the nail. State the independent, dependent and constant variables in this investigation. Independent variable: Number of turns of coil per unit length of the solenoid Dependent variable: Number of pins attracted to the nail Constant variable(s): Current in solenoid; Number of pins used; Orientation of the nail; Horizontal distance between the nail and pins length of thread, L mass of bob, m

8 (C) Outline an investigative procedure to investigate the problem/question Once we have identified the various variables, the next step is to describe the procedure to investigate the relationship given in the question. The following are the items to be included in the procedure: Constant variable(s): To state the variable(s) ( and describe how to keep them constant if the question asked for it). Independent variable: To include the following details: 1. measuring instrument to be used 2. how to measure the variable 3. how to vary the variable (to obtain several values of it) 4. how to manipulate to the form to plot on the graph, if necessary Dependent variable: To include the following details: 1. measuring instrument to be used 2. how to measure the variable 3. indicate to repeat the steps for the same value of the independent variable to find the average value of the measurement for dependent variable Repeat: the steps described for both independent and dependent variables above. Wide (range): the range of values for the independent variable to be conducted for the experiment (do not need to state the range itself). Seven To state that seven sets of data to be collected i.e. conduct the experiment over seven distinct values of the independent variable. EXAMPLE For the rod rolling down the slope, we describe the procedure as follows: 1. The constant variables are initial speed of the marble and the angle of the slope. 2. The independent variable is D, distance travelled by the rod along the slope. 3. Use the metre rule to measure D. We can vary D by changing the starting position of the rod released along the slope. 4. The dependent variable is the time, t for the rod to roll down the distance D along the slope. 5. Use a stopwatch to record the time, t for the rod to roll down the slope for a specific distance, D. We then square t itself to find t2. 6. Repeat step 5 for the same value of D to find the average value of t2. 7. Repeat steps 3 to 6 for a wide range of D to get seven sets of values for D and t2.

9 PRACTICE C1 Describe an experiment to test if the square of the period of a pendulum, T2 is directly proportional to the length of its string, L. 1. Set up the apparatus as shown in the diagram. (Note: We can use the diagram if it is already given in th