Tuesday, September 11, 2012

JAMSASC: Lesson (Significant Figures)

Topic: Significant Figures

Specific Objectives: Students should be able to :
1. State the number of significant figures in a number.
2. Express a number to a given number of significant figures.

Strategies: Discussion, Classwork, Demonstration, Video.

Teaching Aids: Overhead Projector, IBT

Instructional Materials: PowerPoint Presentation, CXC/CSEC Physics Textbook

Presentation: In Physics significant figures are a representation of the precision of a measuring instrument, therefore 2.0 and 2.00 taken as readings from 2 different instruments suggest that 2.00 was taken using an instrument of greater precision.

Development and summary of lesson: The lesson will be in the form of a discussion/lecture. The lesson will begin with the teacher giving a summary of what will be done in class. The teacher will discuss the importance of significant figures in physics. Students will then be shown two videos from Youtube on how to determine significant figures. Two examples will be done to show how we round off numbers to a given number of significant figures. The students will then be asked to give answers to similar examples. The lesson will continue with the teacher going through the different rules governing how the number of significant figures in a number is determined. Several examples of the different cases will be done and the teacher will then give the students some questions to do on their own.

Evaluation of Lesson and assignment given: Questions will be set to test the students understanding of what was done. The students work will be collected and marked and the answers discussed at a later date.

Significant Figures - Rules

Significant figures are critical when reporting scientific data because they give the reader an idea of how well you could actually measure/report your data. Before looking at a few examples, let's summarize the rules for significant figures.

1) ALL non-zero numbers (1,2,3,4,5,6,7,8,9) are ALWAYS significant.

2) ALL zeroes between non-zero numbers are ALWAYS significant.

3) ALL zeroes which are SIMULTANEOUSLY to the right of the decimal point AND at the end of the number are ALWAYS significant.

4) ALL zeroes which are to the left of a written decimal point and are in a number >= 10 are ALWAYS significant.

A helpful way to check rules 3 and 4 is to write the number in scientific notation. If you can/must get rid of the zeroes, then they are NOT significant.Examples: How many significant figures are present in the following numbers?