Physics 121, Sections 9, 10, 11, and 12 Lecture 2 Announcements Lectures available on the web(short version) For over-enrollment please go to the physics office P107 aboratory sessions start next week Gotomywebsitewww.phys.uconn.edu/-rcote Syllabus+ homeworks lectures, etc WebAssign: ready Friday night gotowww.webassign.netandlogin username: first letter of first name plus last name e.g. John Fernando Lachance: lachance 》 institution: uconn > password: your People Soft ID #(with the initial0') Physics 121: Lecture 2, Pg 1
Physics 121: Lecture 2, Pg 1 Physics 121, Sections 9, 10, 11, and 12 Lecture 2 Announcements Lectures available on the web (short version) For over-enrollment please go to the Physics office P107 Laboratory sessions start next week Go to my web site www.phys.uconn.edu/~rcote Syllabus + homeworks + lectures, etc. WebAssign: ready Friday night … go to www.webassign.net and log in » username: first letter of first name plus last name » e.g. John Fernando Lachance: jlachance » institution: uconn » password: your PeopleSoft ID # (with the initial “0”)
Physics 121, Sections 9, 10, 11, and 12 Lecture 2 Today's Topics Chapter 1 Units significant digits Strategy to solve problems Chapter 2: Forces and vectors Types of forces Newton's Laws of motion Net force and vector addition Contact force and tension Physics 121: Lecture 2, Pg 2
Physics 121: Lecture 2, Pg 2 Physics 121, Sections 9, 10, 11, and 12 Lecture 2 Today’s Topics: Chapter 1: Units + significant digits Strategy to solve problems Chapter 2: Forces and vectors Types of forces Newton’s Laws of motion Net force and vector addition Contact force and tension
Significant Figures The number of digits that matter in a measurement or calculation When writing a number, all non-zero digits are significant Zeros may or may not be significant those used to position the decimal point are not significant those used to position powers of ten ordinals may or may not be significant in scientific notation all digits are significant Examples 1 sig fig 40 ambiguous, could be 1 or 2 sig figs 4.0×1012 sig figs 0.0031 2 sig figs 3.03 3 sig figs Physics 121: Lecture 2, Pg 3
Physics 121: Lecture 2, Pg 3 Significant Figures The number of digits that matter in a measurement or calculation. When writing a number, all non-zero digits are significant. Zeros may or may not be significant. those used to position the decimal point are not significant. those used to position powers of ten ordinals may or may not be significant. in scientific notation all digits are significant Examples: 2 1 sig fig 40 ambiguous, could be 1 or 2 sig figs 4.0 x 101 2 sig figs 0.0031 2 sig figs 3.03 3 sig figs
Significant Figures When multiplying or dividing, the answer should have the same number of significant figures as the least accurate of the quantities in the calculation When adding or subtracting, the number of digits to the right of the decimal point should equal that of the term in the sum or difference that has the smallest number of digits to the right of the decimal point Examples 2X3.1=6 3.1+0.004=3.1 4.0×101÷2.04×102=1.6X10 Physics 121: Lecture 2, Pg 4
Physics 121: Lecture 2, Pg 4 Significant Figures When multiplying or dividing, the answer should have the same number of significant figures as the least accurate of the quantities in the calculation. When adding or subtracting, the number of digits to the right of the decimal point should equal that of the term in the sum or difference that has the smallest number of digits to the right of the decimal point. Examples: 2 x 3.1 = 6 3.1 + 0.004 = 3.1 4.0 x 101 2.04 x 102 = 1.6 X 10-1
Adding or Subtracting When numbers are added or subtracted. the number of decimal places in the result equal the smallest number of decimal places of any term in the sum X=123:y=535 123.x0 5.35X 128.X Physics 121: Lecture 2, Pg 5
Physics 121: Lecture 2, Pg 5 Adding or Subtracting When numbers are added or subtracted, the number of decimal places in the result equal the smallest number of decimal places of any term in the sum. x = 123; y = 5.35 123.xxx + 5.35x 128.xxx